TASK DEFINITION: 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.
PROBLEM: Which is an example of a chemical reaction?  
 (A) Vinegar added to baking soda forms a gas. (B) Water evaporates into air. (C) Sugar dissolves in water. (D) Corn kernels are crushed to form flour.

SOLUTION: A

PROBLEM: The human immunodeficiency virus (HIV) causes AIDS. The first known human cases AIDS were in Africa in the late 1950s. Since then, tens of millions of people have died from the disease, and tens of millions more people all over the world are infected. Which term best describes the disease AIDS?  
 (A) isolated cases (B) outbreak (C) epidemic (D) pandemic

SOLUTION: D

PROBLEM: An animal has scales and uses only its lungs to exchange gases. What is the animal most likely to be classified as?  
 (A) a fish (B) a reptile (C) a mammal (D) an amphibian

SOLUTION:
B