I am having a hard time explaining to my students when they should keep a preposition at the end of a question. For example:
Mike is from Boston.
Where is Mike from?
George is in the kitchen.
Where is George? (Definitely not Where is George in?-but why?)
John arrived at noon.
When did John arrive? (no preposition)
Alice waited for Sally.
Whom did Alice wait for? (here we keep the preposition. Why?)
Thanks so much!
On its own, where? means in/at/to which place? These prepositions are there not necessary before the word. Other prepositions are.