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.

Industrial halocarbons are effective ozone-depleters for ____ reasons.
two

Hedgehogs give birth to one to ____ babies which are born with the spines just below the skin.
seven

Stroke is our nation's number ____ killer, and a leading cause of disability for older adults.

three