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.

Example Input: Tobias rode his bike on a road for a 2 hr period. On average, he passed a 1 km marker every 3 min during this period. Which of the following was his average speed for this 2 hr period?  
 (A) 10 km/hr (B) 15 km/hr (C) 20 km/hr (D) 25 km/hr
Example Output: C

Example Input: Which physical characteristic of Earth is similar to a physical characteristic of the Moon?  
 (A) its climate (B) its great seas (C) its atmosphere (D) its mountain ranges
Example Output: D

Example Input: Burning fossil fuels produces sulfur dioxide (SO2) and nitrogen oxide (NO). These compounds react with water vapor to produce acid rain. What is the most likely effect of acid rain on the environment where it falls?  
 (A) The plants and animals in lakes and ponds will be harmed. (B) The soil in the area will become more alkaline. (C) The thickness of the ozone layer will decrease. (D) Levels of air pollution will increase.
Example Output:
A