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: An enclosed 20 mL metal cylinder was filled with a gas sample at room temperature. The sample then was transferred to an empty 40 mL enclosed container, also at room temperature. After being transferred, the volume of the gas was  
 (A) 10 mL. (B) 20 mL. (C) 30 mL. (D) 40 mL.

Answer: D


Question: What has occurred when bubbles form in a liquid that is being heated?  
 (A) Oxygen is absorbed from the air. (B) Heat is radiating in the liquid. (C) The boiling point has been reached. (D) Molecular stability in the liquid is increasing.

Answer: C


Question: Which number is closest to the estimated number of stars in the Milky Way galaxy?  
 (A) 200 thousand (B) 200 million (C) 200 billion (D) 200 trillion

Answer:
C