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]: Variable stars fall into ____ major physical classifications.
[EX A]: four

[EX Q]: All matter exists in ____ dimensional space, both internal and external.
[EX A]: three

[EX Q]: Most swimmers workout twice a day, at least for ____ hours.
[EX A]:
four