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.

Hypertension afflicts about ____ in four American adults, both men and women, of all ages.
one

Amphibians are the first true vertebrates with ____ limbs.
four

Orangutans give birth only once every eight or ____ years.

nine