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]: Plants growing in a pond release a gas that fish need to survive. Which gas do the plants release that fish use?  
 (A) helium (B) hydrogen (C) nitrogen (D) oxygen
[A]: D


[Q]: Helen is preparing a presentation about objects in the solar system. She includes facts about the order of the planets and their distances from the Sun. Which statement could she include in an accurate presentation?  
 (A) Mars is closer to the Sun than Earth. (B) Neptune is one light-year from the Sun. (C) Jupiter is farther from the Sun than Uranus. (D) Earth is one astronomical unit from the Sun.
[A]: D


[Q]: A sample of sulfur forms crystals when it  
 (A) melts. (B) freezes. (C) evaporates. (D) condenses.
[A]:
B