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.

[EX Q]: Which process in the water cycle returns water from the surface of Earth to the atmosphere?  
 (A) condensation (B) evaporation (C) precipitation (D) runoff
[EX A]: B

[EX Q]: When the cardboard cone of a radio speaker vibrates, it produces a sound in the air around it. The cone produces this sound by transferring which of the following to the air around it?  
 (A) heat (B) current (C) wave motion (D) magnetic force
[EX A]: C

[EX Q]: Students are investigating the physical properties of three solid mixtures by placing each solid mixture in liquid water. What physical property are the students testing?  
 (A) solubility (B) conductivity (C) boiling point (D) melting point
[EX A]:
A