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]: During which process does a caterpillar become a butterfly?  
 (A) fertilization (B) metamorphosis (C) asexual reproduction (D) biological adaptation
[EX A]: B

[EX Q]: When the roller coaster rolls onto a flat section of track, what force would ultimately bring it to a stop if no other forces are added?  
 (A) gravity (B) weight (C) friction (D) acceleration
[EX A]:
C