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 drug company developed a pill to reduce cases of stomach virus. To test the medication, half of the participants got the pill with the new medicine and half got a sugar pill. Which term best identifies the participants who got a sugar pill?  
 (A) control (B) experimental (C) dependent variable (D) independent variable
[A]: A


[Q]: A light-year is a measure of  
 (A) time. (B) energy. (C) distance. (D) direction.
[A]: C


[Q]: An increase of carbon dioxide in Earth's atmosphere is most likely to have which effect?  
 (A) decreased variations in day length (B) increased average air temperature (C) increased burn rate for incoming meteoroids (D) decreased rate of ozone layer destruction
[A]:
B