Human biology class

At the end of the human biology class, the lecturer
conducted a quick question and answer session to check that
everyone had been listening to his lesson.
“You over there, the girl in red,” he said pointing, “which
part of the body becomes 10 times its normal size under
emotional stress?”
Flushed with embarrassment, the girl refused to answer, so
another student volunteered.
“The pupil of the eye, Sir.”
“Correct,” replied the lecturer and he turned to the girl,
saying, “Young lady, your refusal to answer my question
indicates three things. One, you haven’t been listening to my
lecture, two, you are obsessed with s*x, and three, you are
going to be very disappointed.”