What "imaginary" number is defined as the square root of -1?

More Questions:

How many different railroads can be bought in the game of Monopoly?

What kind of beans are dropped into a Sambuca?

What is the NATO phonetic alphabet word for "Y"?

The hymn for what branch of the US military begins with the line: "From the halls of Montezuma"?

The US Army's elite 101st Airborne Division is known as the "Screaming" what?

Christmas Island is a territory belonging to which country?

What country borders Guatemala to the west?

What abbreviation comes from libra, meaning pound in Latin?

What is the only insect that can turn its head?

How many episodes of the TV show "All in the Family" were made?

What's the appropriate stage name of musician Richard Melville Hall?

Abe Vigoda played what well known TV character on the program "Barny Miller"?

In what country was Che Guevara born?

What branch of Christianity introduced the Advent calendar?

Easter Island is part of which country?