for green minded persons only

2 kids were lying on bed under a blanket.

1st kid; i'm a boy, and you?

2nd kid: i don't know.

1st kid: wait! i'll check!

(he went under the blanket and said "you're a girl")

2nd kid: how did you know?

1st kid: 'coz my socks are blue and your's are pink! :))