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.

Elves are the first of the ____ families of fairy People.
eight

Natural ytterbium is a mixture of ____ stable isotopes, with seven other unstable isotopes known.
seven

Viruses reproduce via ____ basic steps.

four