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.

Some people routinely sleep only ____ hours a night but feel fine during the day.
four

Elephants give birth to ____ calf every four to nine years on average.
one

Mechanical digestion occurs as ____ strong layers of muscle contract to produce a churning motion.

three