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.

Martin is writing a report for science class about how the tilt of Earth affects living organisms. Which subject should Martin include in his report that is directly affected by Earth's tilt?  
 (A) night and day (B) cloud formation (C) phases of the Moon (D) changing of the seasons
D

Living things are classified as producers or consumers according to  
 (A) their speed of movement (B) the size of their communities (C) how they obtain food (D) how they reproduce
C

One substance found on Earth is more stable as an elemental gas than as part of a solid compound. As a result, this substance is very abundant in the atmosphere. Which substance exhibits these traits?  
 (A) argon (B) chlorine (C) nitrogen (D) oxygen

C