You are given a science question (hard-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 timber company is dividing a 10,000 hectare forest into 5 sections. Which unit is most appropriate to use when showing the area of the divided sections?  
 (A) square inches (in.^2) (B) square meters (m^2) (C) square kilometers (km^2) (D) square centimeters (cm^2)
[EX A]: C

[EX Q]: Joanne's science teacher cautioned the class to be skeptical when learning about new scientific discoveries. Why is it important to be skeptical about new discoveries in science?  
 (A) because many scientific discoveries are not based on facts (B) because most scientific discoveries have no scientific value (C) because most scientists make errors when formulating scientific discoveries (D) because all scientific discoveries must be examined critically before they can be accepted
[EX A]: D

[EX Q]: Two populations of reef fish live in biological coexistence with each other. Which sentence best describes their relationship?  
 (A) The species compete with each other. (B) One species preys on the other. (C) The species ignore each other. (D) One species benefits from the other.
[EX A]:
C