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.

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
D

Which is a major difference between the life cycles of different types of plants?  
 (A) the way they die (B) the energy they use (C) the way they reproduce (D) the way they make food
C

Scientists think that dolphins and whales may have evolved from a common ancestor. What evidence supports this hypothesis?  
 (A) They swim the same way. (B) They eat the same food. (C) They live in the same area of the ocean. (D) They have similar anatomies.

D