Instructions: 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.
Input: A gasoline is advertised as "releasing fewer pollutants" when it is used in cars. For this claim to be accurate, what has most likely happened to the gasoline?
(A) Its acidity has been increased. (B) More oxygen has been dissolved in it. (C) Impurities have been removed. (D) Its molecules have higher chemical energies.
Output:
C