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.

Let me give you an example: Female snakes incubate eggs inside of their bodies, giving birth to live young of ____ or more.
The answer to this example can be: ten
Here is why: Snakes give birth to minimum ten young ones so ten is a correct answer.

OK. solve this:
Several countries conduct time use surveys every ____ years.
Answer:
five