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:
Why would animals most likely have to leave an area during a drought?  
 (A) to find mates (B) to find shelter (C) to escape predators (D) to find water and food

Ex Output:
D


Ex Input:
Oxygen reacts with iron to produce rust and with hydrogen to produce water. Which statement describes both reactions?  
 (A) A different mixture is formed in each case. (B) A different solution is formed in each case. (C) Both a change of state and of elements is involved. (D) New molecules are formed but the same elements exist.

Ex Output:
D


Ex Input:
In most animals, combinations of various tissues make up functional units called  
 (A) epithelial cells. (B) organs. (C) organ systems. (D) populations.

Ex Output:

B