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]: 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]: A student hypothesizes that algae are producers. Which question will best help the student determine if this is correct?  
 (A) Do algae consume other organisms? (B) Which organisms consume algae? (C) Do algae use sunlight to make food? (D) Could an ecosystem survive without algae?
[A]: C


[Q]: A city has an outbreak of a disease that affects an unusually large portion of its population at the same time. Which term best describes the outbreak?  
 (A) pandemic (B) plague (C) epidemic (D) infection
[A]:
C