When do you use WHOSE and when do you use WHO’S?
Whose [THINK: possessive]
Who’s [THINK: contraction (‘)]
“Whose and who’s are commonly confused terms because they sound alike. Luckily, the distinction between them is relatively straightforward.
“Who’s is a contraction of who is or who has…”
“…whose is a possessive pronoun….”
[read more about it on blog.dictionary.com]