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.

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
C

One advantage of a hand lens over a microscope is that the hand lens  
 (A) is easier to carry on field investigations. (B) is less likely to be infected by bacteria. (C) makes very tiny objects appear larger. (D) produces a more accurate image.
A

Several types of mechanisms in the body regulate the rate of chemical reactions in the digestive system. Among the most important are feedback systems, which control the release rate of  
 (A) lipids. (B) enzymes. (C) nucleic acids. (D) carbohydrates.

B