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.

[EX Q]: Food waste is transformed into soil-like humus in three to ____ days.
[EX A]: seven

[EX Q]: Marine biologists have ____ theories on why whales breach.
[EX A]: two

[EX Q]: Equids have ____ basic social systems.
[EX A]:
two