You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Ex Input:
Which of the following is the best example of potential energy?
(A) a fallen rock (B) a burning match (C) a liter of gasoline (D) a red-hot piece of iron

Ex Output:
C

Ex Input:
The incompleteness of the fossil record results primarily from which phenomenon?
(A) the frequency and irregular timing of organism speciations (B) the metamorphosis of most sedimentary rock by heat and pressure (C) the geologically rapid cycling of crust material back into the mantle (D) the rarity with which organic remains are exposed to fossil-forming conditions

Ex Output:
D

Ex Input:
Vehicle exhaust contains a form of pollution called particulate matter. Technologies are being developed to reduce the amount of particulate matter in exhaust. A vehicle that produces less particulate matter would have the greatest impact on which aspect of human health?
(A) heart health (B) respiratory health (C) the rate of birth defects (D) weight and physical fitness

Ex Output:
B