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]: What happens at the boiling point of a substance?  
 (A) liquid becomes a gas (B) solid becomes a gas (C) liquid becomes a solid (D) solid becomes a liquid
[A]: A


[Q]: The changing appearances of the nighttime sky over the surface of Earth and eclipses of the Moon have provided evidence that  
 (A) Earth is a sphere. (B) Earth supports life. (C) Earth has a layered atmosphere. (D) Earth is covered mostly with water.
[A]: A


[Q]: When nearly vertical rays of solar energy strike a region of the Earth, that area has warm temperatures. What region of the Earth gets nearly vertical rays of solar energy year around?  
 (A) Equator (B) Australia (C) United States (D) North and South Poles
[A]:
A