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 will result in the least gravitational attraction?  
 (A) two 2g objects 2 meters apart (B) two 2g objects 4 meters apart (C) two 1g objects 6 meters apart (D) two 1g objects 8 meters apart

Ex Output:
D


Ex Input:
How are green plants an important part of the carbon dioxide-oxygen cycle?  
 (A) They add oxygen to the soil. (B) They release oxygen into the air. (C) They fix carbon dioxide in the soil. (D) They store carbon dioxide in roots.

Ex Output:
B


Ex Input:
What is one way plants and animals are different?  
 (A) Plants do not need minerals, and animals do. (B) Plants produce their own food, and animals do not. (C) Plants do not produce oxygen, and animals do. (D) Plants need sunlight, and animals do not.

Ex Output:

B