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]: Natural ytterbium is a mixture of ____ stable isotopes, with seven other unstable isotopes known.
[EX A]: seven

[EX Q]: Alcohol content is ____ to three times more than beer.
[EX A]: two

[EX Q]: Natural copper contains ____ isotopes.
[EX A]:
two