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.

The incompleteness of the fossil record results primarily from which phenomenon?  
 (A) the frequency and irregular timing of organism speciations (B) the metamorphosis of most sedimentary rock by heat and pressure (C) the geologically rapid cycling of crust material back into the mantle (D) the rarity with which organic remains are exposed to fossil-forming conditions
D

Fertilizers added by farmers to the soil contain high amounts of nitrates. How do fertilizers affect the nitrogen cycle?  
 (A) More nitrates are available for plants to absorb. (B) More nitrates are available for animals to eat. (C) More nitrogen gas is released into the atmosphere. (D) More nitrogen is converted by bacteria into nitrates.
A

The shape of the moon appears to change regularly during each month. Which of the following best explains why the shape of the moon appears to change?  
 (A) The Earth turns on its axis. (B) The Moon turns on its axis. (C) The Moon orbits around the Earth. (D) Clouds cover the Moon.

C