This is a bit of a trick question, as "sat" is already a homophone of itself. It sounds the same as the past tense of the verb "sit", but it is also the past tense of the verb "sat", which means to place something down.
For example:
* She sat down on the chair. (Past tense of "sit")
* The dog sat the bone on the floor. (Past tense of "sat")
Both "sat" and "sit" are pronounced the same, making them homophones.