17.
When you do not know the time, and “ask a policeman” what o’clock it is, why are you like the Viceroy of India?
18.
What is the question to which “yes” is the only possible reply?
19.
What is that which will go up a pipe down, but will not go down a pipe up; or will go down a pipe down, but not up a pipe up, and yet when it has gone up a pipe or down a pipe, will go up or down?