You are given a science question (hard-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 Input:
A cupful of water and a similar cupful of gasoline were placed on a table near a window on a hot sunny day. A few hours later it was observed that both the cups had less liquid in them but that there was less gasoline left than water. What does this experiment show?
(A) All liquids evaporate. (B) Gasoline gets hotter than water. (C) Some liquids evaporate faster than others. (D) Liquids will only evaporate in sunshine. (E) Water gets hotter than gasoline

Ex Output:
C

Ex Input:
Several horses grazed in a fenced area across from a home. On rainy days, soil would wash down a slope and run toward the home. After the horses were moved a few years later, the soil no longer washed down when it rained. What could account for this change?
(A) The grass grew and kept the soil intact. (B) The fence kept the soil contained. (C) The soil was completely gone. (D) The amount of rain decreased.

Ex Output:
A

Ex Input:
When a mixture of oxygen and hydrogen is ignited in a test tube, the reaction shown occurs. Hydrogen + Oxygen -> Water + Energy What happens to the total mass of the contents of the test tube?
(A) The total mass increases. (B) The total mass decreases. (C) The total mass remains the same. (D) Part of the mass is changed to heat energy.

Ex Output:
C