Question

why was hanks brother moth born with dark wings?
soot from an increasing number of factories
it was a response to his changing environment (darker trees)
he had the gene for darker pigmentation
rewatch

Explanation:

The question is about the reason for a moth having dark wings, which relates to genetics (having the gene for darker pigmentation) rather than environmental factors causing a direct response (moths don't change wing color in response to environment during their lifetime, and soot doesn't cause birth with dark wings). The correct reason is genetic - the moth had the gene for darker pigmentation.

Answer:

He had the gene for darker pigmentation (the option with this text)