"Who has given it to him?"
Translation:Wie heeft het aan hem gegeven?
The aan het construction is used to indicate a continuous tense. Why is it used here?
There's no continuous tense with "aan het" in this particular sentence. There's "het" which means "it" and there's "aan" which means "to." A sentence with the "aan het" construction would look like this: Ik ben aan het schrijven (aan het does not mean to and it here) = I am writing.
I've seen 'hem' replacing 'het' in certain contexts. So I simply put that and the continuous tense together and viola, the question. In hindsight, I see the mistake I made. There is no continuous tense involved, as you mentioned, thanks :)