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]: Fertilizers added by farmers to the soil contain high amounts of nitrates. How do fertilizers affect the nitrogen cycle?  
 (A) More nitrates are available for plants to absorb. (B) More nitrates are available for animals to eat. (C) More nitrogen gas is released into the atmosphere. (D) More nitrogen is converted by bacteria into nitrates.
[EX A]: A

[EX Q]: Solids, liquids, and gases are all different states of which of the following?  
 (A) mass (B) matter (C) weight (D) volume
[EX A]: B

[EX Q]: What is the main function of a plant stem?  
 (A) to collect pollen from other plants to make seeds (B) to absorb water and plant nutrients from the soil (C) to carry food and water to the rest of the plant (D) to make food for the plant
[EX A]:
C