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]: What happens at the boiling point of a substance?  
 (A) liquid becomes a gas (B) solid becomes a gas (C) liquid becomes a solid (D) solid becomes a liquid
[EX A]: A

[EX Q]: Which is the best tool for measuring the temperature of lake water?  
 (A) Meter stick (B) Balance (C) Graduated cylinder (D) Thermometer
[EX A]: D

[EX Q]: When using a hot plate, students should not  
 (A) leave the hot plate unattended. (B) follow the teacher's instructions. (C) pull back hair or clothing to avoid contact. (D) wear insulated gloves when holding metal materials.
[EX A]:
A