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:
Lichens are symbiotic organisms made of green algae and fungi. What do the green algae supply to the fungi in this symbiotic relationship?  
 (A) carbon dioxide (B) food (C) protection (D) water
answer:
B


question:
In Maryland, most bears have thick, dark fur. Which statement best explains how dark fur helps bears survive in the forests of Maryland?  
 (A) Dark fur is lightweight. (B) Dark fur scares enemies. (C) Dark fur helps bears hide. (D) Dark fur keeps bears cool.
answer:
C


question:
How is the mass of an atom calculated?  
 (A) add the number of protons to the number of electrons (B) add the number of protons to the number of neutrons (C) subtract the number of protons from the number of neutrons (D) subtract the number of electrons from the sum of protons and neutrons
answer:

B