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 action creates competition between environmental concerns and economic gains?  
 (A) protecting endangered wildlife (B) reintroducing wildlife into their natural habitats (C) using forest land to build homes (D) using city buses for transportation
[EX A]: C

[EX Q]: Cells take in food for energy. The part of the cell that aids in digestion of the food is the lysosome. What is the main role of lysosomes in the process of food digestion?  
 (A) building proteins (B) breaking down wastes (C) controlling the activities of the cell (D) converting energy from one form into another
[EX A]: B

[EX Q]: The Sun is an example of which of the following?  
 (A) comet (B) planet (C) galaxy (D) star
[EX A]:
D