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]: Which is the best unit to measure distances between Earth and other solar systems in the universe?  
 (A) miles (B) kilometers (C) light years (D) astronomical units
[EX A]: C

[EX Q]: Which example best illustrates an action-at-a-distance force?  
 (A) lifting a box (B) an apple falling (C) pulling a nail out of wood (D) a car moving along a flat surface
[EX A]: B

[EX Q]: Many different plant and animal species live in the Amazon rainforest. Which is the most likely result of large areas of deforestation in the Amazon rainforest?  
 (A) an increase in animal populations (B) a decrease in oxygen production (C) an increase in precipitation (D) a decrease in pollutants
[EX A]:
B