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.

Sharks have a total of ____ senses, five of which are involved in locating food.
six

Irrigated land is almost ____ times as productive as rainfed cropland.
three

Natural samarium is a mixture of several isotopes, ____ of which are unstable with long half-lives.

three