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]: If an atom has two protons and three electrons, then the atom is  
 (A) positively charged. (B) negatively charged. (C) radioactive. (D) neutral.
[EX A]: B

[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]: Company X makes 100 custom buses each year. Company Y makes 10,000 of one type of bus each year. Which of the following is the most likely reason a customer would buy a bus from company X instead of company Y?  
 (A) to keep the cost of the bus low (B) to ensure that the bus will be easy to replace (C) to provide ideas about how the bus will be built (D) to ensure that people know how to drive the bus
[EX A]:
C