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]: 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
[EX A]: D

[EX Q]: Humans use both renewable and nonrenewable resources. Which human activity uses a nonrenewable resource?
(A) building houses with wood (B) using natural gas to heat homes (C) using solar energy to power lights (D) producing electricity from flowing water
[EX A]: B

[EX Q]: What geographic obstacle causes water to condense in an air mass as the air mass moves?
(A) forests (B) oceans (C) prairies (D) mountains
[EX A]:
D