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]: A pot is heated on a stove. Which process causes the metal handle of the pot to also become hot?  
 (A) combustion (B) convection (C) radiation (D) conduction
[EX A]: D

[EX Q]: The excessive use of nitrogen-based fertilizers causes runoff that increases the nitrogen content of lakes and bays. These nitrogen compounds directly affect the aquatic ecosystems by  
 (A) interfering with the water cycle. (B) decreasing the predator population. (C) increasing the rate of algae growth. (D) causing aquatic animals to grow larger.
[EX A]: C

[EX Q]: Photosynthesis is the process that converts carbon dioxide and water into  
 (A) carbon and oxygen. (B) sugar and hydrogen. (C) sugar and oxygen. (D) nitrogen and carbon.
[EX A]:
C