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.
One example is below.
Q: Which event can cause a large rock to become soil over time? 
 (A) decaying (B) an earthquake (C) a landslide (D) weathering
A: D
Rationale: Under the action of heat, cold, rain, wind, and other atmospheric factors, the rock breaks down physically into small fragments that become the parent material of the soil. Also, atmospheric factors change according to weather.
Q: The sunlight used for solar heating is a resource that is best considered to be  
 (A) artificial. (B) renewable. (C) inexhaustible. (D) nonrenewable.
A:
C