Whose and Who's
It is important to distinguish between these two. The grammar checker on MS Word is not good at spotting problems with these two and sometimes advises the incorrect option.
"Who's" is the contracted form of "who is" or "who has".
Remember that contracted words should not be used in formal essays. The only time they can legitimately appear is in direct speech.
"Who's going to the cinema today?" he asked. (who is)
"Trevor, who's going to play James Bond, is an awful actor," he retorted. (who is)
"Who's got the chocolate?" (who has)
"Whose" is a possessive form meaning "of whom" or "belonging to who" and is used in the following way:
Whose books are these?
The men, whose lives were ruined, claimed compensation from the government.
I do not know whose shoes smell worst.
If you are in any doubt, consider whether the who's/whose you are using can be replaced by who is or who has. If it can, then you need "who is", if not you will need "whose".
Test your understanding of who's/whose with this exercise.