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.

Which of the following is most likely to disrupt the natural balance in an ecosystem?  
 (A) introduction of a non-native species (B) reduced daylight hours during winter (C) preventing the cutting of trees in forests (D) riverbank erosion resulting from springtime flooding
A

During which process does a caterpillar become a butterfly?  
 (A) fertilization (B) metamorphosis (C) asexual reproduction (D) biological adaptation
B

Which tool would be most useful in studying the living organisms the students collected from the pond?  
 (A) balance (B) pH meter (C) microscope (D) thermometer

C