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.

[Q]: In 1971, the bones of an extinct flying dinosaur were discovered. This kind of discovery helps everyone learn more about  
 (A) impact of humans on Earth. (B) effect of gravity on animals. (C) history of animal species on Earth. (D) likelihood that dinosaurs will reappear.
[A]: C


[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
[A]: C


[Q]: Structures in the universe are grouped into large systems, each of which are made up of smaller systems. Which of the following is the largest system of which Earth is only a very small part?   
 (A) Jovian planets (B) Halley's comet (C) Milky Way galaxy (D) Orion's belt
[A]:
C