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]: What gas in the air do we need to breathe in order to live?  
 (A) nitrogen (B) oxygen (C) carbon dioxide (D) hydrogen (E) water vapor
[EX A]: B

[EX Q]: Which is a process that occurs during photosynthesis?  
 (A) Plants take in oxygen and release sugar. (B) Plants take in sugar and release minerals. (C) Plants take in minerals and release carbon dioxide. (D) Plants take in carbon dioxide and release oxygen.
[EX A]: D

[EX Q]: A student is visiting a local limestone quarry and finds fossils of seashells. The quarry is located hundreds of miles from the ocean. The fossils best indicate that  
 (A) this area was once below sea level. (B) global temperature changed over time. (C) erosion took place after a flood. (D) volcanic activity affected the area.
[EX A]:
A