You are given a science question (easy-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 Q]: When a hammer strikes a nail, the nail  
 (A) exerts balanced forces that helps it from moving. (B) exerts a force equal to the weight of the hammer. (C) exerts an unbalanced force that changes its velocity. (D) exerts an equal and opposite force back on the hammer.
[EX A]: D

[EX Q]: Compared to Earth, the Moon is  
 (A) drier. (B) larger. (C) heavier. (D) brighter.
[EX A]: A

[EX Q]: A generator converts mechanical energy to electrical energy by using a conducting metal loop turning in a  
 (A) magnetic field. (B) gravitational field. (C) steel sphere. (D) copper sphere.
[EX A]:
A