Prepositions at the End of Questions

Who are they with?
Who did you sit with at the meeting?
What are you working on?
What are you looking at?
What was the meeting about?
Where is she from?
Where did this come from?
Which school did you go to?
Which restaurant should we eat at?
Which candidate are they going to vote for?
Whose house did they go to?
Whose problems were they talking about?
Whose party were they at last night?