Free Scientific Reasoning MCQs with Answers

291. How does aquatic life survive freezing temperatures?

• A. They have cold-shock proteins which allow them to survive via hibernating while they are frozen
• B. In water bodies, only the top layer freezes in winters, allowing aquatic life to survive
• C. The aquatic life migrates out before the water bodies freeze
• D. They do not survive but they lay their eggs before winter starts. The off-spring then recreate the population from scratch

Explanation: Only the top layer of a lake or river freezes, underneath the frozen upper layer the water remains in its liquid form and does not freeze. Also, oxygen is trapped beneath the layer of ice. As a result, fish and other aquatic animals find it possible to live comfortably in the frozen lakes and ponds.

292. Why is the greenhouse effect given that name?

• A. The greenhouse effect leads to global warming and the solution to global warming is to go green i.e. to plant more trees. Hence it is called the greenhouse effect
• B. The heating effect caused by greenhouse gases is similar to that caused by the glass in a greenhouse
• C. The scientist who invented the term loved the color green
• D. None of the above options are correct

Explanation: The process is called the greenhouse effect because the exchange of incoming and outgoing radiation that warms the planet works in a similar way to a greenhouse.

293. Why should you not stand close to a fast-moving train?

• A. The fast-moving train creates a strong air pressure which can cause you to fall and hurt yourself
• B. The fast movement in front of your eyes will make you feel dizzy and cause you to faint
• C. The impact from any object falling out of the train can be extremely injurious due to the velocity of the train
• D. It's just a disciplinary measure, there is no harm in standing close to a fast-moving train

Explanation: When a fast-moving train passes on a rail, the velocity of the air stream in between the rail and the by-stander standing near the rail is larger compared to the velocity of air streams on the other side of the by-stander away from the rail. According to Bernoulli's theorem, the pressure of air will become low between person and rail and is high on the other side of the by-stander. As a result of this pressure difference, a thrust acts on them, pushing them towards the rail side leading to possible accidents.

294. How does soap work to clean our hands?

• A. The slippery nature of the soap causes the germs to slip off
• B. The soap traps germs and dirt and is washed off with them
• C. The soap disintegrates grease on the skin due to its non-polar tail
• D. The soap produces free radicles which destroy the germs on our hands

Explanation: The following picture shows the explanation to this question:

295. Order the following steps to separate a mixture of sodium chloride, sand and iron. I- Mix in water II- Evaporate III- hold a magnet bar above the mixture/solution IV- Filter and dry filtrate

• A. I>II>III>IV
• B. II>III>IV>I
• C. I>III>IV>II
• D. III>I>IV>II

Explanation: To obtain dry iron, we first hold a magnet above the mixture. We then mix the remaining salt and sand into water. We filter out and dry the sand. Following this, we evaporate the water to obtain dried sodium chloride.

296. 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 to the strings and a speaker connected to it amplifies the volume
• B. The tension in the strings is especially higher so it 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 voice

Explanation: Sound-hole, a hollow chamber, is an essential component of stringed musical instruments, and enhances the sound radiation in the lower octave by introducing a natural vibration mode called air resonance.

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

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

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

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

299. Farmer Brown was observing the mice that live in his field. He discovered that all of them were either fat or thin. Also, all of them had either black tails or white tails. This made him wonder if there might be a link between the size of the mice and the color of their tails. So he captured all of the mice in one part of his field and observed them. Below are the mice that he captured Is there a link between the size of the mice and the color of their tails?

• A. appears to be a link
• B. appears not to be a link
• C. cannot make a reasonable guess
• D. The size causes the tail color to change

Explanation: With very few exceptions, fat mice usually have black tails and small mice had white tails. However, this relationship is not enough to establish causality

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

• A. It provides air resistance to objects entering Earth, hence burning and destroying meteors before they can land on the surface
• B. Ozone disintegrates into oxygen which is needed for cellular respiration
• C. Ozone captures free radicals such as chlorine which may damage human tissues if inhaled
• D. The ozone layer absorbs harmful radiation which may cause skin cancer if exposed to

Explanation: The stratospheric ozone layer is Earth's "sunscreen" - protecting living things from too much ultraviolet radiation from the sun, and preventing the development of cancers.