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.

[Q]: When do mutations help make an ecosystem more sustainable?
(A) when mutations decrease the number of individuals in an ecosystem (B) when mutations increase the number of individuals in an ecosystem (C) when mutations decrease the number of species in an ecosystem (D) when mutations increase the number of species in an ecosystem
[A]: D

[Q]: Which would be a safe practice to exercise during laboratory investigations?
(A) using open flames to heat all materials (B) keeping your cell phone on the laboratory countertop (C) knowing where your instructor/laboratory leader is at all times (D) removing your safety glasses when moving from station to station
[A]: C

[Q]: Scientists often use mathematical models and computer simulations to study systems. What is the main advantage of using these techniques for studying the spread of infectious diseases?
(A) to reduce the amount of work for all involved (B) to reduce the cost of conducting experiments on people (C) to obtain results quickly in a short period of time (D) to perform experiments that would be irresponsible using human subjects
[A]:
D