Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Question: When two haploid gametes unite during fertilization they form what? Answer: a diploid cell
diploid cell that forms when two haploid gametes unite during fertilization.

Question: Fertilization is the union of a sperm and egg, resulting in the formation of what? Answer: a zygote
Fertilization is the union of a sperm and egg, resulting in the formation of a zygote.

Question: Smog is a visible form of what? Answer: air pollution
Smog clouds the city of Los Angeles, California. Visible air pollution in the form of smog is a sign that the air is unhealthy.