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: Why should plants be included in investigations about the water cycle?  
 (A) Plants speed up the water cycle by removing carbon from the air. (B) Plants start the water cycle when they make water in photosynthesis. (C) Plants are part of the water cycle through the process of transpiration. (D) Plants stop the water cycle because they absorb it and stop the flow to streams.

SOLUTION: C

PROBLEM: Which force produces energy as heat?  
 (A) pull (B) gravity (C) friction (D) magnetic

SOLUTION: C

PROBLEM: Plant cells use special parts to capture sunlight. The parts use the sunlight to make food. Where will you find the most of these parts in a plant?  
 (A) roots (B) stems (C) leaves (D) flowers

SOLUTION:
C