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]: Pigs grow very quickly and are normally ready for sale at ____ to six months of age.
[EX A]: four

[EX Q]: Some botanists recognise ____ botanical varieties.
[EX A]: two

[EX Q]: Natural magnesium contains ____ isotopes.
[EX A]:
three