instruction:
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:
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
answer:
D

question:
Which action involving a pulley system requires the least amount of force?
(A) using several pulleys together instead of a single pulley (B) using a fixed pulley instead of a moveable pulley (C) pulling a long rope instead of a short rope (D) pulling a rope up instead of down
answer:
A

question:
Fruit flies reproduce by sexual reproduction. What percent of genes does a fertilized egg of a fruit fly receive from one parent?
(A) 25% (B) 50% (C) 75% (D) 100%
answer:
B