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.

Example Input: Many scientists are convinced that an increase of certain gases in the atmosphere is affecting global temperatures. What makes this hypothesis difficult to prove?
(A) Trees absorb these gases. (B) Global temperatures are rising. (C) Many variables affect global temperatures. (D) Many human activities produce these gases.
Example Output: C

Example Input: The incompleteness of the fossil record results primarily from which phenomenon?
(A) the frequency and irregular timing of organism speciations (B) the metamorphosis of most sedimentary rock by heat and pressure (C) the geologically rapid cycling of crust material back into the mantle (D) the rarity with which organic remains are exposed to fossil-forming conditions
Example Output: D

Example Input: Which term best describes the movement of water through cell membranes?
(A) respiration (B) osmosis (C) mitosis (D) condensation
Example Output:
B