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Free Scientific Reasoning MCQs with Answers

334 Scientific Reasoning MCQs from Analytical and Logical Reasoning, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Scientific reasoning evaluates hypotheses through observations, variables, controls, measurements and experimental results. Questions involve identifying independent and dependent variables, recognising a fair test, interpreting tables or graphs, distinguishing evidence from opinion, and deciding whether data supports, rejects or leaves a hypothesis unresolved.

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334 questions · page 4 of 17

61. Why does a guitar produce such a loud sound but when strings detached from the body produce very little sound?

  • A. There is a microphone attached near the strings, and a speaker connected to it amplifies the volume
  • B. The tension in the strings is exceptionally high, which produces a louder sound
  • C. Special kinds of strings are used which enable a louder sound to be produced
  • D. Resonance in the soundhole allows for amplification of the sound

Explanation: The correct answer is that the guitar's resonance amplifies the sound. The soundhole and the hollow body of the guitar act as a resonating…

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Correct answer: Resonance in the soundhole allows for amplification of the sound

62. Why are soldiers required to break their march before stepping onto any bridge?

  • A. To prevent the noise created from marching disturbing the life beneath the bridge
  • B. To prevent injury from marching on an incline
  • C. To prevent the bridge collapsing due to resonance
  • D. To not produce sound which may easily be heard by enemies on the other side

Explanation: At a certain point, the bridge would start oscillating to the same rhythm as that of the marching steps.

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Correct answer: To prevent the bridge collapsing due to resonance

63. Which phenomenon is underplay when we tune to different stations on radio?

  • A. Refraction
  • B. Frequency Modulation
  • C. Stationary waves
  • D. Resonance

Explanation: When we tune to different stations, we actually change the frequency of carrier wave at which our system will resonate at.

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Correct answer: Resonance

64. How does a microwave primarily work?

  • A. It cooks food via conduction
  • B. It cooks food via convection
  • C. It cooks food via resonance
  • D. It cooks food via radiation

Explanation: Microwaves operate by emitting electromagnetic waves that match the natural resonant frequency of water molecules.

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Correct answer: It cooks food via resonance

65. Which of the following produces/is a transverse wave?

  • A. Clapping hands horizontally
  • B. Clapping hands vertically
  • C. Water waves
  • D. Pulling and pressing a spring

Explanation: Water waves are transverse waves since the motion of particles is perpendicular to the wave's direction of travel, creating surface…

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Correct answer: Water waves

66. Why doesnt water leave a bucket despite being upside down when we are swirling it as shown?

  • A. The centrifugal force pushes the water away from the center of gravity, countering gravity.
  • B. Water has stuck to the bottom of the bucket.
  • C. The inertia of the water causes it to move sideways instead of moving in the direction of gravity.
  • D. The water has developed a gravitational attraction with the bucket and does not fall.

Explanation: The water remains in the bucket during swirling due to its inertia. As the bucket moves in a circular path, the water tends to continue…

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Correct answer: The inertia of the water causes it to move sideways instead of moving in the direction of gravity.

67. Given below is a food web. Population of which of the following will see a decrease if the number of frogs undergo a drastic decrease?

  • A. Mouse
  • B. Grasshopper
  • C. Rabbit
  • D. Birds

Explanation: The number of birds will decrease since snakes can only feed on birds now, so will consume more of them.

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Correct answer: Birds

68. A student was provided with a slide to view under a microscope. He was not able to spot a nucleus but could see a cell wall, a whip-like structure at one corner of the cell. Which of the following can be the slide that the student was presented?

  • A. E.coli from the stomach
  • B. Ciliated cells of the trachea
  • C. Red blood cells
  • D. Fungi mycelium

Explanation: E.coli being a prokaryote lacks nucleus, has a cell wall and may have a flagella

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Correct answer: E.coli from the stomach

69. An organism has genotype Aa Bb CC Dd. How many different types of combinations are possible for gamete formation?

  • A. 2
  • B. 4
  • C. 8
  • D. 16

Explanation: To determine the number of different types of gamete combinations, examine each gene locus: A, B, and D are heterozygous, meaning they…

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Correct answer: 8

70. If telomerase enzymes are less active than usual, what medical condition will this cause?

  • A. Cancer
  • B. Pneumonia
  • C. Cardiovascular disorders
  • D. Premature aging

Explanation: Reduced telomerase activity results in faster telomere shortening, leading to cellular senescence and ultimately contributing to premature…

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Correct answer: Premature aging

71. Due to positioning of the fetus, the umbilical cord becomes twisted and fails to function properly. What problem will this causes for the fetus?

  • A. All of the above
  • B. Brain damage from low oxygen supply
  • C. Malnutrition
  • D. Lower birth weight

Explanation: The umbilical cord provides oxygen and nutrients to the fetus. A lack of its functionality would lead to all of the above mentioned symptoms

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Correct answer: All of the above

72. The skeleton of a mamoth was recently recovered from a permafrost mine in the United States. Analysis of the elements in the mammoth showed 1/32th of the expected levels of carbon-14 isotope. If the half life of carbon-14 may be considered to be 5730 years, how many years ago did this mammoth exist?

  • A. 5,730 years
  • B. 11,460 years
  • C. 32,300 years
  • D. 28,650 years

Explanation: Half-life is the amount of time required for a substance to decrease to half its initial value.

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Correct answer: 28,650 years

73. Which of the following is NOT sufficient to measure the resistance of an unknown resistor?

  • A. Battery, voltmeter, ammeter, connecting wires, switch
  • B. Battery, galvanometer, 3 known resistors, switch, connecting wires
  • C. Battery, ohmmeter, connecting wires
  • D. Battery, ammeter, galvanometer, switch, connecting wires

Explanation: The correct answer is Option D. This setup does not have the necessary equipment to measure voltage or resistance directly, as it lacks…

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Correct answer: Battery, ammeter, galvanometer, switch, connecting wires

74. The figure shows Ahmad, standing on an elevator which is moving front he fourteenth floor to the fourth floor. Ahmad initially stood on a weighing scale to see that his mass was 60kg at rest. If the acceleration of the elevator is 2m/s2, what reading does the scale show? (g=10m/s2)

  • A. 60kg
  • B. 72kg
  • C. 48kg
  • D. 80kg

Explanation: When the elevator falls in the direction of gravity, the relative acceleration decreases from 10 to 8m/s2.

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Correct answer: 48kg

75. Why is the ozone layer so important for our survival?

  • A. It provides air resistance to objects entering Earth, causing them to burn up.
  • B. The ozone layer absorbs harmful ultraviolet radiation from the sun.
  • C. Ozone traps harmful chemicals like chlorine to prevent tissue damage.
  • D. Ozone breaks down into oxygen which is essential for breathing.

Explanation: The stratospheric ozone layer is crucial because it acts as Earth's "sunscreen," absorbing the majority of the sun's harmful ultraviolet…

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Correct answer: The ozone layer absorbs harmful ultraviolet radiation from the sun.

76. Erythrocytes are the functional component of blood responsible for the transportation of gasses and nutrients throughout the human body. Their unique shape and composition allow for these specialized cells to carry out their essential functions. Erythrocytes would swell and burst if placed in conditions:

  • A. Temperature of 310 K
  • B. 15% NACL solution
  • C. 0.15% NACL solution
  • D. 15% Hydrochloric acid

Explanation: This is a hypotonic solution (lower concentration of solutes). Hypotonic solutions can cause cells to take in water and swell.

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Correct answer: 0.15% NACL solution

77. How many chain isomers can an aliphatic saturated hydrocarbon with 7 carbons make?

  • A. 7
  • B. 5
  • C. 12
  • D. 9

Explanation: An aliphatic saturated hydrocarbon with 7 carbons is an alkane, represented by the formula C₇H₁₆.

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Correct answer: 9

78. Based on table 1, of the following 4 metals, which has the greatest ability to carry electric current?

  • A. Iron
  • B. Beryllium
  • C. Magnesium
  • D. Tungsten

Explanation: As shown in the table, out of all four metals listed, beryllium has the highest conductivity value i.e 2.81

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Correct answer: Beryllium

79. A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums.Pyrethroids are used as commercial and household insecticides.Pyrethroid is an organic compound produced by the flowers of pyrethrums. Scientists found that even in a bee populated area, the bees were not found near the pyrethrums. After further research they concluded that pyrethroid is a defensive chemical produced by these plants to keep bees away from the flowers by affecting the neurochemical pathway of the bees. Scientists further researched and developed a synthetic pyrethroid and was introduced as an insecticide on a commercial scale to farmers in the early 1900s. Initially it was very successful in keeping insects away. However, after a while the farmers started feeling severe mood swings and nausea on a daily basis. Later, scientists further studied the insecticide and deduced that the insecticide in large quantities also affected the neurochemical pathways of the farmers and reduced the synthesis of a neurotransmitter in the brain. Which neurotransmitter did the Pyrethroid affect in the farmers who used the insecticide in a large quantity

  • A. Acetylcholine
  • B. Calcitonin
  • C. Serotonin
  • D. GABA

Explanation: The information provided suggests that the synthetic pyrethroid affected the neurochemical pathways of the farmers and reduced the…

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Correct answer: Serotonin

80. Ethanol and Propane are both colorless organic substances of a similar molar mass with 2 and 3 carbon atoms respectively. However, despite having a longer carbon chain, propane is a gas and ethanol, having less carbon atoms is a liquid at room temperature. What is the reason behind the differences observed

  • A. Ionic bonding in ethanol
  • B. Greater dispersion forces in ethanol
  • C. Hydrogen bonding between molecules of ethanol
  • D. Dipole forces between the O and H in the ethanol molecule

Explanation: The key factor explaining the difference in physical state between ethanol and propane is the presence of hydrogen bonding in ethanol.

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Correct answer: Hydrogen bonding between molecules of ethanol
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