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 system of the human body provides protection to most of the major organs?  
 (A) skeletal system (B) circulatory system (C) respiratory system (D) muscular system

Ex Output:
A


Ex Input:
Which method is the best safety procedure when working around open flames?  
 (A) wear an acid-resistant apron (B) wash your hands (C) tie back long hair (D) use an electric fan to blow gases from the flame

Ex Output:
C


Ex Input:
The water in a pond gets colder one night. Which tool is best to observe its temperature change?  
 (A) balance (B) magnifying glass (C) ruler (D) thermometer

Ex Output:

D