Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Q: Irrigated land is almost ____ times as productive as rainfed cropland.

A: three
****
Q: Traffic lights have ____ colors.

A: three
****
Q: Hydronic heating has ____ advantages over other types of heating systems.

A:
three
****