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 amphibians reach maturity at three or ____ years.

A: four
****
Q: Potential energy is divided into ____ different types of energy.

A: three
****
Q: Natural palladium contains ____ stable isotopes.

A:
six
****