Who:
* Who is coming to the party? (Refers to a person)
* Who wrote this amazing book? (Refers to a person)
* Who will be responsible for the presentation? (Refers to a person)
Whom:
* Whom did you invite to the dinner? (Refers to a person as the object of a verb or preposition)
* Whom are you talking to? (Refers to a person as the object of a preposition)
* Whom did they choose for the lead role? (Refers to a person as the object of a verb)
Whose:
* Whose car is parked in the driveway? (Refers to possession)
* Whose idea was this? (Refers to possession)
* Whose turn is it to clean the kitchen? (Refers to possession)
What:
* What is your favorite color? (Refers to a thing or idea)
* What did you eat for breakfast? (Refers to a thing)
* What is the meaning of life? (Refers to an idea)
Which:
* Which dress should I wear? (Refers to a specific item from a group)
* Which of these books is yours? (Refers to a specific item from a group)
* Which way should we go? (Refers to a specific option from a set)
Remember: Interrogative pronouns are used to ask questions. They always introduce a question, and they are followed by a question mark.