You are given a science question (hard-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.

Input: Consider Input: The fur of some animals becomes thicker in the winter and is shed in the spring. These observations show how animals
(A) respond to changes in the environment (B) move from place to place to survive (C) store fat for the winter (D) compete with other animals for food

Output: A

Input: Consider Input: What occurs if the body's renal system fails to work?
(A) Gas exchange is impaired. (B) Blood oxygenation no longer occurs. (C) Metabolic waste builds up in the blood. (D) Nutrients are no longer transported to organs.

Output: C

Input: Consider Input: The discovery of fossilized coral reefs on land is evidence that
(A) salt water changes coral into fossils. (B) the reefs formed in a freshwater lake. (C) the sea level has changed over time. (D) coral reefs can form on dry land.
Output: C