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.

Echinoderms have radial symmetry , many having ____ or multiples of five arms.
five

Psychology is founded on ____ false premises that are all humanistic from the core.
eight

Natural erbium is a mixture of ____ stable isotopes .

six