instruction:
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.
question:
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.
answer:
A


question:
Estuaries are marine environments located in areas where fresh water from rivers flow into the ocean. Estuaries are one of the most biologically productive ecosystems. Birds, fish, turtles and many other organisms inhabit these ecosystems. Which will most likely cause changes to estuary habitats on a global scale?  
 (A) decreases in powerful hurricanes (B) decreases in volcanic eruptions (C) increases in earthquakes (D) increases in sea level
answer:
D


question:
The pull of gravity from Earth has the greatest effect on  
 (A) comets. (B) the Sun. (C) asteroids. (D) the Moon.
answer:

D