I'm not sure, but my best answer would be "C". Hope this helps, sorry if it doesn't.
Answer:
A
Explanation:
D is not correct because the atmosphere doesn't expand, C isn't correct because the Sun doesn't heat all the Earth evenly (hence different climates), B is not correct because cold fronts can be singular, so it has to be A
Answer:
Its used as validity, and quality of the articles. The main purpose of it is to filter out poor or invalid articles.
Explanation:
Answer:
examples include, "FF" or "DD", or just two uppercase letters.
Explanation:
