where are you going/where do you come from

[Edison_Chen_e_c]

Why don't we give a "prep" to the sentence:

1.where are you going to?

And why don't we take the "prep" off the sentence:

2.where do you come from?

All in one, I know 'where' is an 'adv' in the first sentence, but why 'where' become a 'pron' in the second one? Can it be a 'pron'?

[Harry Smiith]

[Edison_Chen_e_c]

One more: how should I say,

1.I don't know where he is going.
2.I don't know where he is going to.
3.I don't know where he comes from. (from 'where does he come from')
4.I don't know where he comes. (from 'where does he come from')
5.If I want to know one's nationality, it must be 'Where do you come from', then 'where' here is an 'pron', can it be?