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:
Prolonged exercise stimulates muscle cells to absorb sugar from the blood. This mechanism reduces stress placed on the body by signaling the body to produce  
 (A) insulin. (B) lipids. (C) hemoglobin. (D) hydrochloric acid.

Ex Output:
A


Ex Input:
Which of these warms most of the air, water, and land on Earth?  
 (A) Coal (B) Electricity (C) Sunlight (D) Wind

Ex Output:
C


Ex Input:
Humans use both renewable and nonrenewable resources. Which human activity uses a nonrenewable resource?  
 (A) building houses with wood (B) using natural gas to heat homes (C) using solar energy to power lights (D) producing electricity from flowing water

Ex Output:

B