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 force produces energy as heat?  
 (A) pull (B) gravity (C) friction (D) magnetic

Ex Output:
C


Ex Input:
Which material is the best conductor of electricity?  
 (A) Wood (B) Metal (C) Stone (D) Plastic

Ex Output:
B


Ex Input:
Which of the following was invented by Benjamin Franklin?  
 (A) bifocal lens (B) telescope lens (C) telephone (D) camera

Ex Output:

A