Question

the traveller knocked......the door of the house.(fill the blank with at/on)

Answer 1

hi mate...............

here's ur answer...........!

The Traveller knocked at the door of the house.

Here at is used because this sentence conveys a location.

At is also used to describe something that is happening at the given place.

So here someone is knocking and he is knocking at the door.
Hence we will use at in the given sentence to complete it.

hope it helps ✌️