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]: Joann repeatedly overfed the fish in the pond behind her house. The nitrates from the excess food contributed to an overgrowth of algae. To correct the problem, Joann added more plants to the pond. How will adding more plants help?  
 (A) The plants make the pond look beautiful. (B) The plants will camouflage the green algae. (C) The plants will compete with algae for nutrients. (D) The plants will provide all the food for the fish.
[EX A]: C

[EX Q]: What is the downward movement of water through pores and other spaces in soil due to the force of gravity?  
 (A) percolation (B) evaporation (C) precipitation (D) condensation
[EX A]: A

[EX Q]: A student stands outside on a cold winter day. His hands become cold and he rubs them together to make them warmer. Which statement explains why rubbing his hands together makes them warmer?  
 (A) This action produces thermal energy through friction. (B) This action conducts thermal energy away from the body. (C) This action captures thermal energy from the environment. (D) This action reduces the amount of thermal energy transferred to the air.
[EX A]:
A