In most countries, sex is a proposition.
"Should we?" - "We should."
"Can we?" - "We can."
and many more such infuriatingly cooperative situations.
Sex in India however is a preposition.
"Have you ever done that?"
The standard reply to this question is more or less the same. Open your mouth in the shape of an 'O' and while emitting a steady sound rapidly cup and uncup your hand on your mouth(3 cycles per second should do the trick). The resulting sound should be something like this ...
"You did thataaaa?"
"Tee Hee ... no"