Complete the sentence by choosing the correct option out of those given below:

________ being questioned, he wept.

On

Option 3: "on" is the correct choice

The reason option (3) "on" is the correct choice to complete the sentence is because it is the most appropriate preposition to indicate the specific time or occasion when an action occurs. In this case, the sentence is describing the moment when he wept, which is "being questioned." "On" is used to convey this sense of timing or the specific situation in which the action took place.