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]: 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]: How do traits of animals such as ear shape, nose shape, and hair color most often get passed to offspring?  
 (A) sexual reproduction (B) asexual reproduction (C) adaptation (D) instinct
[A]: A


[Q]: The Halifax River has a major flood plain in Port Orange, Florida. Minerals are deposited into the soil of the flood plain when the water overflows the banks of the river. These minerals can reduce the absorption of the soil in the flood plain and affect the growth of plants in the area. Which best describes the role of the deposited minerals in the flood plain ecosystem?  
 (A) a trophic level (B) a limiting factor (C) a territorial boundary (D) a food-chain component
[A]:
B