You are given a science question (hard-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.

Leucine is one of the amino acids your body needs but cannot make. Which of these happens so that the human body can obtain leucine?
(A) The body converts other amino acids to leucine. (B) The body stores carbohydrates containing leucine. (C) The body breaks down fatty acids to obtain leucine. (D) The body digests protein in food to obtain leucine.
D

A student is investigating different types of trees. Two trees are found to have similar growth rates, temperature ranges, and sizes, but different leaves and flowers. The trees are most likely in
(A) the same species. (B) the same genus. (C) a different kingdom. (D) a different phylum.
B

Which phrase best describes the mass of an object?
(A) the weight of the object (B) the volume of the object (C) the amount of matter in the object (D) the amount of gravitational pull on the object
C