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.

The systems of the human body work together. Which system works with the skeletal system by pulling on the bones to create movement?  
 (A) digestive (B) circulatory (C) muscular (D) nervous
C

Sam looks into a fish pond and points at a goldfish. Sam's grandfather looks where Sam is pointing and tells Sam that the fish is actually in a different location. Which property of light explains why Sam's grandfather is correct?  
 (A) reflection (B) refraction (C) diffraction (D) absorption
B

Which is a physical property of an apple?  
 (A) what color it is (B) how pretty it is (C) how much it costs (D) when it was picked

A