WHO’S key is this? → ❌

WHOSE key 🔑 is this? → ✔

WHOSE crying right now? → ❌

WHO’S (who is) crying? 😭→ ✔

FACT: You can use “whose” with people AND objects:

I know a man *whose* dad is tall. → ✓.

I have a chair *whose* legs are broken. → ✓.

Fact:
In some expressions, English has no prepositions where one may be used in another language; in other expressions the opposite is true.