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.

[EX Q]: A scanning electron microscope is best suited for observing  
 (A) diffraction of light. (B) tectonic features on planets. (C) the surfaces of small objects. (D) topographical features on the ocean floor.
[EX A]: C

[EX Q]: Planting certain crop plants in a field causes a disruption of the natural nitrogen cycle in that field. Which outcome would this disruption most DIRECTLY cause in the field over time?  
 (A) topsoil erodes (B) soil nutrients decrease (C) desert conditions appear (D) atmospheric carbon dioxide increases
[EX A]: B

[EX Q]: In what way do transit systems, such as buses, benefit society?  
 (A) by reducing the amount of pollution (B) by increasing the number of car sales (C) by increasing the amount of carbon dioxide in the air (D) by eliminating the possibility of accidents
[EX A]:
A