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 scientific guess about the cause and effect of an event is called  
 (A) a variable. (B) a theory. (C) a hypothesis. (D) an observation.
[A]: C


[Q]: One of the main causes of acid rain is  
 (A) Waste from nuclear power plants (B) Spills from chemical manufacturing plants (C) Gases from burning fossil fuels (D) Gases from aerosol spray cans
[A]: C


[Q]: A recent study concluded that about 90% of all large predatory fish such as tuna have disappeared from the world's oceans in the past 50 years. Which of these is most likely the direct cause of this loss?  
 (A) Urban development near the coast (B) Commercial harvesting from the ocean (C) Climate change on Earth (D) Acid precipitation over the oceans
[A]:
B