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: Prions are protein molecules which have ____ metastable states.

A: two
****
Q: Beryllium is found in a variety of countries on ____ continents.

A: five
****
Q: Menstrual uncleanness lasts for ____ days.

A:
seven
****