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]: Carolina uses a microscope to view a soil sample taken from her backyard. Which part of the soil would she ONLY be able to see with a microscope?  
 (A) bacteria (B) grass (C) rainwater (D) rocks
[EX A]: A

[EX Q]: Which type of air mass forms over the ocean near the equator?  
 (A) moist and warm (B) moist and cool (C) dry and warm (D) dry and cool
[EX A]: A

[EX Q]: In the past, wild hogs called "javelinas" were seen only in the southern part of New Mexico. Now, javelinas are seen in areas 100 miles further north. What is the most likely cause of this expansion?  
 (A) Javelinas are reproducing less frequently. (B) Environmental conditions have changed. (C) The javelina's genetic traits have mutated. (D) Nutritional requirements of javelinas have changed.
[EX A]:
B