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:
A ball is rolling on the ground. A force pushes the ball in the same direction that it is moving. What happens to the ball?  
 (A) It stops moving. (B) It moves slower. (C) It moves faster in the same direction it was moving. (D) It keeps moving in the same speed and direction.

Ex Output:
C


Ex Input:
What do scientists mean when they refer to a population?  
 (A) all the organisms in an ecosystem (B) all the species that share similar anatomical features (C) all the animals that acquire resources through similar methods (D) all the interbreeding members of a certain species in an ecosystem

Ex Output:

D