instruction:
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.
question:
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
answer:
A


question:
What form of energy is being used when a person pushes a wooden block across the floor?  
 (A) mechanical (B) magnetic (C) sound (D) electrical
answer:
A


question:
Which is an example of melting?  
 (A) Flowing water making a rock smooth (B) A carrot becoming soft when cooked (C) Sugar mixed into tea making the tea sweet (D) Butter changing into liquid in a warm pan
answer:

D