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]: Most healthy men experience about three to ____ erections in their sleep each night.
[A]: five


[Q]: Traffic lights have ____ colors.
[A]: three


[Q]: Normal cells have ____ copies of each gene.
[A]:
two