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.
--------
Question: 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

Answer: B


Question: Bones support the body. What pulls and pushes on bones to move them?  
 (A) blood (B) nerves (C) muscles (D) skin

Answer: C


Question: As a result of human activity, many lakes in Florida have increased levels of nutrients that support algal growth. These algae grow very rapidly, then die and decompose. What impact does this overgrowth of algae most likely have on the lake ecosystem?  
 (A) The number of fish species increases. (B) The volume of lake water increases. (C) The buildup of bottom sediments decreases. (D) The amount of dissolved oxygen decreases.

Answer:
D