Answer:
Which bank is not used for storing money?
4 rubber ducks were floating in the bathtub, 2 floated away and 2 drowned. How many ducks are still alive?
What is the building that you leave without ever having entered.
An archaeologist unearths a coin bearing the inscription "57BC". How does he instantly know that it's a forgery?
There are two sisters: one gives birth to the other and she, in turn, gives birth to the first. Who are the two sisters?
What goes around and around the wood, but never goes into the wood?