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.

[EX Q]: Which is a hypothesis that can be easily tested?  
 (A) The Moon causes high tides. (B) During which season are the tides the highest? (C) What is the phase of the Moon when tides are highest? (D) When the Moon is full, the tides will be at their highest.
[EX A]: D

[EX Q]: Which of these has the greatest capacity for storing thermal energy from the Sun?  
 (A) air (B) land (C) oceans (D) plants
[EX A]: C

[EX Q]: What role do plants have in the carbon cycle?  
 (A) use water and release carbon (B) use sugar and release carbon (C) use carbon and release oxygen (D) use carbon and release nitrogen
[EX A]:
B