Answer:
The sentence that is grammatically incorrect is:
D. Who's jacket is this?
Step-by-step explanation:
"Whose" and "who's" sound exactly the same, which is why they are commonly mistaken for one another. However, their use and meanings are very distinct.
"Whose" indicates possession. When you ask a question with "whose", you want to know who owns something. For example: Whose car is that? --> Who owns that car?
On the other hand, "who's" is the contraction of "who is". There is no sense of possession involved here. When you use "who's", you basically want to know the identity of someone. Example: Who's that man? Who's knocking?
With that in mind, we can choose letter D as the one that is grammatically incorrect.