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:
Which of these reduces the need for people to use nonrenewable resources?  
 (A) recycling paper products (B) watering the lawn once a week (C) designing cars that are fuel efficient (D) using coal to generate electricity

Ex Output:
C


Ex Input:
Which animal is preparing for a seasonal change in the environment?  
 (A) a bat flying at night (B) a deer drinking water (C) an owl eating a mouse (D) a squirrel storing nuts

Ex Output:
D


Ex Input:
The elements carbon, hydrogen, and oxygen are parts of many different compounds. Which explains why these three elements can make so many different compounds?  
 (A) They can be solids, liquids, or gases. (B) They come in different sizes and shapes. (C) They combine in different numbers and ratios. (D) They can be a proton, a neutron, or an electron.

Ex Output:

C