My brother-in-law’s hobby is butterfly collecting. Option A is the answer that properly completes the sentence.
We use apostrophe s (’s), also called possessive ’s, as a determiner to show that something belongs to someone or something.
When we aim to show that something belongs to somebody or something, we have to add an apostrophe + s ('s) to a singular noun and an apostrophe (') to a plural noun.
