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.
Example: Which part of a bicycle BEST moves in a circle?
(A) Seat (B) Frame (C) Foot pedal (D) Kickstand
Example solution: C
Example explanation: Seat, frame and Kickstand are static parts of the bicycle, even when bicycle moves. Foot pedal moves in a circle as bicycle moves.

Problem: Colored alcohol is used in some glass thermometers. When placed in air of different temperatures, the column of alcohol rises or falls in the glass thermometer. Which of the following best explains why the height of the alcohol column changes?
(A) The glass contracts when heated. (B) The alcohol contracts when heated. (C) The glass expands more than the alcohol when heated. (D) The alcohol expands more than the glass when heated.
Solution: D