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.

[Q]: 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
[A]: A


[Q]: On a field trip, a student holds a frog and reports that it has slippery skin. This is an example of  
 (A) a measurement (B) a prediction (C) an explanation (D) an observation
[A]: D


[Q]: The Moon revolves around Earth about once every  
 (A) day. (B) year. (C) week. (D) month.
[A]:
D