1.

What occurs once in a minute, twice in a moment, but never in an hour?

the letter M
a clock
a second

2.

What is coming but will never arrive?

the postman
tomorrow 
the wind

3.

Why is a Math book sad?

it has no parents
it has so many problems
it has no money

4.

How many months have 28 days?

all of them
six months
February

5.

What two words have the most letters?

New York
Alpha Beta
Post Office