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]: How does sedimentary rock form?  
 (A) sediments cool (B) sediments melt (C) sediments separate (D) sediments compress
[EX A]: D

[EX Q]: A girl found the skull of an animal. She did not know what the animal was but she was sure that it preyed on other animals for its food. What clue led to this conclusion?  
 (A) The eye sockets faced sideways. (B) The skull was much longer than it was wide. (C) There was a projecting ridge along the top of the skull. (D) Four of the teeth were long and pointed. (E) The jaws could move sideways as well as up and down.
[EX A]: D

[EX Q]: Which process drives most of the ATP synthesis in a chloroplast?  
 (A) flow of protons across an electrochemical gradient (B) flow of tRNA across an electrochemical gradient (C) exposure of ADP to electromagnetic waves (D) exposure of carbohydrates to electromagnetic waves
[EX A]:
A