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 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:
In a lab investigation, a student notes that two metal blocks have the same mass. Based on this observation, if the two blocks were put on opposite sides of a balance, they would best represent  
 (A) balanced forces. (B) unbalanced forces. (C) equal and opposite reactions. (D) objects in motion.

Ex Output:
A


Ex Input:
When a person's arm touches something hot, the muscles in the arm react to pull the arm away. Which body system alerts the muscles to react?  
 (A) Nervous (B) Digestive (C) Circulatory (D) Respiratory

Ex Output:

A