I contributed this question to a trivia night once.

The 21M cap of bitcoin is..

A) written in code explicitly, Bitcoin checks regularly if the cap is not broken.
B) written in code explicitly, Bitcoin does not check regularly if the cap is broken.
C) implicit, Bitcoin checks regularly if the cap is not broken.
D) implicit, Bitcoin does not check regularly if the cap is broken. 

 It's not that difficult but I think it's a fine question for intermediate level.