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]: Blood donors can give blood every ____ weeks, or six times a year.
[A]: eight


[Q]: Copper has ____ naturally occurring isotopes.
[A]: two


[Q]: Most polar bears sleep for ____ to eight hours at a stretch and they take naps, too.
[A]:
seven