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]: A large number of species on Earth became extinct during a short time period about 65 million years ago. Based on this pattern of extinction, which is the most likely cause?  
 (A) gradual climate change (B) continued climate stability (C) sudden global climate change (D) gradual ecosystem succession
[EX A]: C

[EX Q]: Which of these elements is found in the greatest amount in organisms?  
 (A) carbon (B) iron (C) lead (D) neon
[EX A]: A

[EX Q]: Scientists found fish fossils in the desert. What do the fossils tell about this environment when the fish were alive?  
 (A) There was a forest with large trees. (B) There were lakes with water plants. (C) There were mountains with glaciers. (D) There was a desert with large rocks.
[EX A]:
B