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.

What gas in the air do we need to breathe in order to live?  
 (A) nitrogen (B) oxygen (C) carbon dioxide (D) hydrogen (E) water vapor
B

Historically, how has the compass been used?  
 (A) for navigation (B) to predict weather (C) to measure temperature (D) for mineral identification
A

Which condition is most likely to cause the formation of a temperature inversion?  
 (A) rapid cooling of the ground at night (B) high wind on a sunny morning (C) saturation of soil with warm rain (D) rapid collision of warm and cold fronts

A