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.

[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
[A]: B


[Q]: Parents with freckles often have children with freckles. This occurs because  
 (A) freckles develop from light. (B) certain foods cause freckles. (C) certain habits cause freckles. (D) freckles are an inherited trait.
[A]: D


[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
[A]:
D