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.

Q: 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

A: A
****
Q: Early scientists most likely saw a discharge of electricity for the first time when observing a  
 (A) waterfall (B) rainbow (C) lightning storm (D) volcano erupting

A: C
****
Q: A marsh in your neighborhood dried up during a long, hot summer. This is most likely to cause which of the following changes in the neighborhood?  
 (A) an increase in the number of bats (B) a decrease in the number of mosquitoes (C) an increase in the number of insect-eating birds (D) a decrease in the number of Japanese beetles

A:
B
****