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:
A condition in bees called "colony collapse disorder" occurs when worker bees leave the hive to collect nectar and never return. How would a decline in the bee population most likely affect a farm ecosystem?  
 (A) There would be a decrease in soil thickness. (B) There would be a decline in fruit production. (C) There would be an increase in plant diseases. (D) There would be an increase in insect pest populations.
answer:
B


question:
Use of nuclear fuel would most likely reduce human contributions to which environmental problem?  
 (A) ozone thinning (B) landfill creation (C) shoreline erosion (D) greenhouse heating
answer:
D


question:
A group of students are researching changes in climate in their region. Which of these would best provide evidence of changes in temperature and rainfall over a period of years?  
 (A) tree rings (B) pollen samples (C) harvest production (D) carbon dating
answer:

A