TASK DEFINITION: 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.
PROBLEM: 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

SOLUTION: A

PROBLEM: A scientist is searching for areas where new solar systems might form. What feature is the scientist looking for?  
 (A) a star similar to our Sun (B) a cloud of dust and gas (C) an oxygen-rich atmosphere (D) a gravitational acceleration of 9.8 m/sec2

SOLUTION: B

PROBLEM: Acid rain caused by industrial pollution greatly reduces the number of trees in a forested region that is home to a particular species of bird. How might this decrease in the number of trees most likely affect this bird population?  
 (A) The population will adapt to ground dwelling. (B) The population will decrease due to lack of resources. (C) The population will stabilize when it moves to another region. (D) The population will increase as predators move out of the region.

SOLUTION:
B