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.

[Q]: Which activity is an example of a good health habit?  
 (A) riding a bicycle without a helmet (B) smoking cigarettes (C) wearing a hat while in the Sun (D) eating with dirty hands
[A]: C


[Q]: A container is filled with a mixture of sand and an unknown substance. What should a student do to determine whether iron particles are in the mixture?  
 (A) heat the mixture (B) filter the mixture (C) pour water into the mixture (D) pull a magnet through the mixture
[A]: D


[Q]: The average rainfall in Nevada is about 7 inches per year. The most likely reason for the low amount of rainfall is the  
 (A) high elevations of deserts. (B) location north of the equator. (C) lack of moisture in the air. (D) great distance from the ocean.
[A]:
C