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:
The fusion reaction that fuels the Sun converts hydrogen into  
 (A) carbon. (B) iron. (C) neon. (D) helium.

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


Ex Input:
Human actions can change the rate at which soil erodes. Which of the following would most likely slow the rate of soil erosion?  
 (A) applying nitrogen-rich fertilizers (B) keeping grasses trimmed short (C) building houses on stilts (D) planting trees along cliffs

Ex Output:

D