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 Q]: Energy appears in many forms. What form of energy is lightning?  
 (A) electrical energy (B) mechanical energy (C) magnetic energy (D) sound energy
[EX A]: A

[EX Q]: The systems of the human body work together. Which system works with the skeletal system by pulling on the bones to create movement?  
 (A) digestive (B) circulatory (C) muscular (D) nervous
[EX A]: C

[EX Q]: Technological advances are allowing scientists to develop methods for replacing abnormal human genes with healthy copies of the same genes. Which is the most likely use for this gene therapy?  
 (A) killing viruses (B) healing wounds (C) treatment of airborne infections (D) treatment of inherited diseases
[EX A]:
D