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]: Which material is most easily recycled at school?  
 (A) plastic wrap (B) notebook paper (C) ice cream sticks (D) rubber erasers
[EX A]: B

[EX Q]: When manned space exploration began, NASA used the gravity assist concept so that spacecraft could conserve fuel. Which statement explains why the gravity assist concept was useful for spacecraft to successfully travel and return to Earth?  
 (A) It gave spacecraft a timed trajectory. (B) It ensured spacecraft would return home safely. (C) It was helpful in planning spacecraft trajectories. (D) It ensured spacecraft would avoid being pulled into the sun.
[EX A]: C

[EX Q]: An idea that the universe originated with an explosion is supported by repeated observations of light from distant galaxies traveling away from Earth. An idea that has been tested repeatedly and is supported by repeated results is most likely a  
 (A) hypothesis. (B) theory. (C) law. (D) fact.
[EX A]:
B