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.

Cytochrome oxidase consists of two cytochromes and ____ copper atoms.
two

Deer mice have four toes on the forefeet and ____ toes on the hind feet.
five

Roots grow mostly sideways and can extend up to ____ times the height of the tree.

three