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]: Which best describes a scientific theory?  
 (A) It is still being tested. (B) It is true, once written. (C) It is different for each continent. (D) It is determined in a court of law.
[A]: A


[Q]: Auroras occur where Earth's magnetosphere traps high-energy particles in which region of the atmosphere?  
 (A) troposphere (B) stratosphere (C) thermosphere (D) exosphere
[A]: C


[Q]: Clara says that her school is in a desert. Which fact about her schoolyard most helps her claim?  
 (A) The schoolyard has few trees. (B) The schoolyard has rocks and sand. (C) The schoolyard gets warm in the summer. (D) The schoolyard gets little rain during the year.
[A]:
D