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]: Two atoms of oxygen combine to form pure oxygen gas. What is the electrical charge of the O_{2} molecules?  
 (A) positive (B) negative (C) neutral (D) variable
[A]: C


[Q]: What is a common use of the mineral graphite?  
 (A) to make glass (B) as a source of iron (C) to make pencil leads (D) as a household cleaner
[A]: C


[Q]: Kudzu vines grow by climbing and wrapping around trees. Trees covered by kudzu can die because they are starved of sunlight. What type of relationship exists between the trees and the kudzu growing on them?  
 (A) competition (B) mutualism (C) parasitism (D) predator-prey
[A]:
A