This excludes your girlfriend of coz... 
I mean
normal friends or close friends. Reason I am asking this is because
I had a strange encounter. I am quite close to a group of friends
of 3 girls, which is why we decided to be project mates.
This incident happened over the resent weekend on Sunday, when we
had to do a science project which is due very soon, for
presentation. Concidentally, the topic is on the reproductive
system of male and female.
The gathering place is at one of my friend's house. To cut the long
story short, after we completed the project, the girls asked me a
very funny question - if I had masturbated before. I was pretty
shocked at their words. I was thinking perhaps we have reached an
age of maturity, and besides, being science students, they might be
just curious to find out more about the opposite sex. I replied
with a "yes", and the next question pop up after a while - if I am
able to show them the whole masturbation process.
I regarded the whole thing as a joke and dismissed the whole issue.
But now to think back, maybe I should have done it. 
Is it common nowadays for such questions to be pop up?
