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:
The fusion reaction that fuels the Sun converts hydrogen into  
 (A) carbon. (B) iron. (C) neon. (D) helium.

Ex Output:
D


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

Ex Output:
B


Ex Input:
Land forms are created through destructive forces such as weathering. Which of these is an example of physical weathering?  
 (A) acid rain (B) erosion (C) hydrolysis (D) oxidation

Ex Output:

B