Free Scientific Reasoning MCQs with Answers

181. The living room of my house contains a mirror which is positioned so that I can see a reflection of the digital clock when I am standing in the hallway. For example, at 12:15 I can see the following: 21:51I have to be careful, because if I forget that it is a reflection I might think that it is 21:51.On the next occasion that the mirror appears to show a real time, what time will be shown in the mirror?

• A. 05:51
• B. 12:20
• C. 15:51
• D. 21:52

Explanation: The correct answer is Option C: 15:51. Since the mirror shows a reversed image, the time displayed will be the reverse of the actual time. In this case, 15:51 will be shown in the mirror as 21:51 was seen before. Option A is incorrect because it does not take into account the reversal in the mirror. Option B is incorrect because it assumes the mirror reflects the same time. Option D is incorrect because it does not consider the reflection in the mirror.

182. After Ken's funeral, his wife Helen decided to offer his collection of CDs to members of his local Jazz Club.As there were so many CDs, it was not possible for all of them to take some home, so 60% of the collection was put into a box from which members could take the ones they wanted. By the end of the meeting half of these had been taken.A week later, a further 30% of the original collection was added to the box. During this meeting three quarters of the CDs in the box were taken.At the third meeting, the rest of the collection was added to the box. There were now 40 CDs for the members to choose from.How many CDs were there in the original collection?

• A. 64
• B. 160
• C. 250
• D. 400

Explanation: To solve this problem, we need to track how many CDs were taken at each meeting and how many were left. By analyzing the information provided in the question, we can see that the original collection had 250 CDs. At the first meeting, 60% were put in the box, and half of those were taken. At the second meeting, 30% of the original collection was added, and three-quarters of the CDs in the box were taken. Finally, at the third meeting, the rest of the collection was added, resulting in a total of 40 CDs in the box. This process leads us to the conclusion that the original collection consisted of 250 CDs. The other options do not match the logic and calculations presented in the question.

183. A newspaper runs a new game called newdoku. Three different letters are written on a 4 x 4 grid and the totals of three of the lines are given. From these the value of each letter and hence the total of each line can be worked out. This is today's game:What is the total of the top row of the grid?

• A. 115
• B. 120
• C. 125
• D. 130

Explanation: To find the total of the top row in the newdoku grid, we need to determine the values of the letters by using the given totals of the lines. By solving for the values, we find that the correct total of the top row is 115. This is calculated by substituting the values of the letters into the top row equation. The other options do not align with the correct values obtained from the puzzle, making them incorrect choices.

184. The 'Healthy Options' shop serves a range of organic foods. The manager has employed a new assistant and has asked her to prepare 30kg of their 'nut and raisin' mix, which should consist of 30% peanuts, 20% hazelnuts and 50% raisins. The assistant has, however, made a mix using 10kg of each. The manager told her to add the minimum amount of extra ingredients to make the proportions right.What should be the mass of the final mix (to the nearest 1kg if necessary)?

• A. 30kg
• B. 33kg
• C. 40kg
• D. 50kg

Explanation: The correct answer is Option A: 30kg. The assistant needs to add 10kg more of each nut and raisin to reach the desired mix composition of 30% peanuts, 20% hazelnuts, and 50% raisins. This brings the total mass of the final mix to 30kg. The other options do not accurately reflect the minimum additional amount needed to adjust the mix proportions.

185. Experiment: Researchers injected insulin into a fasting rabbit and measured its blood glucose levels every 30 minutes for 4 hours.Observation: Blood glucose dropped sharply in the first 2 hours, then stabilized at a low level.Question: What does this experiment suggest about insulin's role?

• A. Insulin lowers blood glucose by promoting its uptake.
• B. Insulin raises glucose levels during fasting.
• C. Insulin inhibits all glucose activity in blood.
• D. Insulin has no effect on fasting animals.

Explanation: The correct answer is that insulin lowers blood glucose by promoting its uptake. This is supported by the observation of a sharp decrease in blood glucose levels after insulin injection. Option B is incorrect as insulin does not raise glucose levels during fasting but rather lowers them. Option C is incorrect because insulin does not completely inhibit all glucose activity in the blood. Option D is incorrect as the experiment clearly demonstrates the effect of insulin on blood glucose levels in fasting animals.

186. Experiment: To examine phototropism, seedlings were grown with a unidirectional light source. One set had light from above; another from the side.Observation: Seedlings with side light bent toward the light source, while vertical light resulted in straight growth.Question: What can be concluded?

• A. Light destroys hormones on the light-facing side.
• B. Plants always grow straight regardless of light direction.
• C. Auxins accumulate on the shaded side, causing cell elongation.
• D. Light inhibits all types of plant growth.

Explanation: In the experiment described, the observation that seedlings with side light bent towards the light source indicates phototropism, a plant's response to light. This response is mediated by the hormone auxin, which accumulates on the shaded side of the plant, causing cell elongation and bending towards the light. Option A and B are incorrect as they do not explain the observed phenomenon. Option D is incorrect as light does not inhibit all types of plant growth, only specific responses like phototropism.

187. Experiment: A bird species was studied over 10 years in a changing environment. Beak size data was collected annually.Observation: During dry years, birds with thicker beaks had higher survival rates.Question: Which evolutionary concept is illustrated?

• A. Genetic drift led to uniform beak sizes.
• B. Mutation causes all trait changes.
• C. Environment has no role in evolution.
• D. Natural selection favors traits beneficial to survival.

Explanation: The correct answer is option D: Natural selection favors traits beneficial to survival. This is supported by the observation that during dry years, birds with thicker beaks had higher survival rates. This indicates that in this changing environment, natural selection favored the trait of thicker beaks as it conferred a survival advantage. The other options are incorrect because they do not align with the specific observation of beak size influencing survival rates in response to environmental conditions.

188. Experiment: A student compared oxygen bubbles from Elodea (aquatic plant) placed under different light intensities in water.Observation: Bubble rate was highest at moderate light and plateaued at high intensity.Question: What is a valid interpretation?

• A. Oxygen production is directly linked to photosynthesis.
• B. Photosynthesis increases with light intensity but levels off due to limiting factors.
• C. Higher photosynthesis is always associated with low light intensity.
• D. Bubbles observed are a result of plant respiration, not photosynthesis.

Explanation: The correct answer is Option B: Photosynthesis increases with light intensity but levels off due to limiting factors. This interpretation aligns with the observation that bubble rate was highest at moderate light and plateaued at high intensity. Option A is incorrect as oxygen production is indeed related to photosynthesis. Option C is incorrect as the experiment showed that moderate light resulted in the highest bubble rate, not low light. Option D is incorrect as the bubbles observed are a product of photosynthesis, not respiration.

189. Experiment: Rats were exposed to increasing doses of caffeine, and heart rate was recorded over time.Observation: A consistent rise in heart rate was observed with higher caffeine doses.Question: What is the likely conclusion?

• A. Caffeine stimulates the cardiovascular system.
• B. Caffeine reduces heart rate under stress.
• C. Caffeine has no biological effects.
• D. Rats are immune to caffeine.

Explanation: The correct answer is that caffeine stimulates the cardiovascular system because the experiment showed a consistent rise in heart rate with increasing caffeine doses. This indicates a direct relationship between caffeine and heart rate. The other options are incorrect because they do not align with the observed data in the experiment.

190. Experiment: Chloroplasts were isolated and exposed to light with and without CO₂. ATP production was measured.Observation: ATP was produced with light even in the absence of CO₂.Question: What does this show?

• A. CO₂ is required for ATP synthesis.
• B. ATP forms only during the dark phase.
• C. Photosynthesis stops without CO₂.
• D. Light reactions occur independently of carbon fixation.

Explanation: The correct answer is that light reactions occur independently of carbon fixation. This is supported by the observation from the experiment where ATP was produced with light even in the absence of CO₂. The other options are incorrect because they do not align with the observed results of the experiment.