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]: In a lab investigation, a student notes that two metal blocks have the same mass. Based on this observation, if the two blocks were put on opposite sides of a balance, they would best represent
(A) balanced forces. (B) unbalanced forces. (C) equal and opposite reactions. (D) objects in motion.
[EX A]: A

[EX Q]: When iron combines with oxygen in a moist environment, rust forms because of a
(A) chemical reaction. (B) physical reaction. (C) change in density. (D) change in temperature.
[EX A]: A

[EX Q]: Growth and repair in multicellular organisms are the result of
(A) excretion (B) locomotion (C) cell division (D) decomposition
[EX A]:
C