All of them.
Answer is 2. One to change the lightbulb while the other screams "REPOST"
Only one. But they have to sit in the dark room for a year, first, to make sure that the lightbulb is out.
A: Why are you asking me that question Can't you see I'm busy!
A Brazilian
Irrelevant, you will be assimilated!
Existence is futile.