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.

Ex Input:
Cell division is necessary for an organism to
(A) obtain nutrients. (B) grow and reproduce. (C) make proteins. (D) conserve matter and energy.

Ex Output:
B

Ex Input:
The yellow-throated longclaw is a bird that lives on the dry savanna of Africa. It looks almost exactly like another bird, the western meadowlark of North America. Although the birds look very similar, they are not even in the same taxonomic family. Scientists think the birds look alike because the two species developed under similar environmental pressures, even though they developed thousands of miles apart. Which process does their development demonstrate?
(A) sexual selection (B) disruptive selection (C) divergent evolution (D) convergent evolution

Ex Output:
D

Ex Input:
What keeps stars such as the Sun from collapsing from their own self-gravity?
(A) the centrifugal force created by rapid rotation (B) the electrical repulsion of nuclei in the plasma (C) the gravitational pull created by orbiting planets (D) the outward pressure created by nuclear fusion

Ex Output:
D