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 Q]: During which season of the year would a rabbit's fur be thickest?  
 (A) fall (B) spring (C) summer (D) winter
[EX A]: D

[EX Q]: Which unit is used to express the amount of energy in food?  
 (A) Calorie (B) degree Celsius (C) milliliter (D) gram
[EX A]: A

[EX Q]: What motion causes day and night?  
 (A) revolution of Earth (B) revolution of the Moon (C) rotation of Earth (D) rotation of the Moon
[EX A]:
C