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]: You wish to closely observe a small insect. Which tool is the best to use?  
 (A) a balance (B) a test tube (C) a telescope (D) a magnifying glass
[A]: D


[Q]: Which two protein molecules are essential for muscle contraction and relaxation?  
 (A) actin and myosin (B) collagen and tubulin (C) hemoglobin and myoglobin (D) amylase and polymerase
[A]: A


[Q]: A few types of birds live in the same ecosystem. Which of these characteristics would most likely affect how they compete with each other for food?  
 (A) the types of nests they build (B) the lengths of their tails (C) the shapes of their beaks (D) the colors of their feathers
[A]:
C