Question

fill with preposition he is sitting....... the table​

Answer 1

he is sitting under the table

or

he is sitting on the table

Answer 2

However, if something is “on the table” it means that it is on top of the table. So, if you say that you are sitting on the table, or on the desk, it means you are sitting on top of the table.

So, sitting at the table, is when you're sitting in your chair, and the table's in front of you.