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]: What is the function of skin on the human body?
(A) Skin has pores that help the body sense odor. (B) Skin protects the body from harmful substances. (C) Skin brings oxygen directly into the body's bloodstream.
[EX A]: B

[EX Q]: While conducting an experiment on gravity, what will be needed to ensure the safety of students?
(A) quiet zones (B) drop zones (C) heavy objects (D) frictionless surfaces
[EX A]: B

[EX Q]: Chloroplasts in cells make it possible for the cells to
(A) reproduce. (B) hold their rigid shape. (C) absorb and excrete materials. (D) carry out photosynthesis.
[EX A]:
D