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:
Which object is best used to demonstrate the bending of light as it passes through a substance?  
 (A) convex lens (B) flat mirror (C) opaque rod (D) concave mirror

Ex Output:
A


Ex Input:
Which form of energy are x rays and ultraviolet light?  
 (A) nuclear (B) heat (C) electromagnetic (D) chemical

Ex Output:
C


Ex Input:
In which of the following are nutrients directly absorbed from the bloodstream?  
 (A) cell (B) organ (C) organisms (D) tissue

Ex Output:

A