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]: Kim lost her hammer outside. When she found it a few months later, some parts of the metal were covered with flaky, brown rust. Which type of change occurred when rust formed on the hammer?  
 (A) chemical (B) electrical (C) thermal (D) physical
[EX A]: A

[EX Q]: Which is the greatest benefit of sexual reproduction?  
 (A) capable of reproducing by meiosis (B) ability to reproduce without a mate (C) ability to produce genetically different offspring (D) capable of producing offspring genetically identical to parent
[EX A]: C

[EX Q]: A student is measuring the speed at which a ball rolls down a ramp. Which unit of measurement is the student most likely using to describe the speed of the ball?  
 (A) meter per liter (B) seconds per gram (C) milligrams per liter (D) centimeters per second
[EX A]:
D