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 Input:
A student notices a paw print while walking in a park. The paw print could be considered a fossil if the print was in ___.
(A) rock (B) topsoil (C) thick mud (D) loose sand

Ex Output:
A

Ex Input:
Two identical books are on opposite ends of a table. Which of these would increase the gravitational force exerted between the two books?
(A) decrease the distance between the books (B) decrease the mass of the books (C) decrease the mass of the table (D) decrease the temperature in the room

Ex Output:
A

Ex Input:
Which characteristic of sound makes it possible for bats to fly in the dark without hitting any objects?
(A) refraction (B) reflection (C) conduction (D) amplification

Ex Output:
B