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:
One example of a living thing is  
 (A) air (B) water (C) a rock (D) a worm

Ex Output:
D


Ex Input:
How much time is required for a bicycle to travel a distance of 100 m at an average speed of 2 m/s?  
 (A) 0.02 s (B) 50 s (C) 100 s (D) 200 s

Ex Output:
B


Ex Input:
The amount of gravitational attraction between the Moon and an astronaut standing on its surface depends on the astronaut's distance from the center of the Moon and the astronaut's  
 (A) height. (B) mass. (C) shape. (D) weight.

Ex Output:

B