Who
That's my mother.
Who is that?
The quiz is Monday.
When is the quiz?
My favorite restaurant is in Uptown.
Where is your favorite restaurant?
The capital of the United States is Washington D.C.
What is the capital of the United States?
Class is over at 12:10.
When is class over?
I usually take one suitcase with me when I travel.
How many suitcases do you usually take with you? (when you travel)