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.

[Q]: Most organ systems are operational in the fetus by ____ to six months.
[A]: four


[Q]: Wood consists of ____ distinct fuels.
[A]: two


[Q]: Plants produce ____ types of stems.
[A]:
two