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]: International mail consists of ____ categories of mail.
[A]: three


[Q]: Kinetic energy consists of ____ types of energies.
[A]: three


[Q]: Triangles are polygons of ____ sides.
[A]:
three