Smoking after ?

Two teens had been lovers for a few weeks, but the boy was
always after the girl to quit smoking. One afternoon, she lit up
after some love making, and he said, "You really ought to quit."

She, getting tired of his nagging, said, "I really enjoy a good
cigarette after sex."

He replied, "But they stunt your growth." She asked if he ever
smoked, and he replied that he had never.

Smiling and lifting her gaze to his groin, she said, "So, what's
your excuse then?"