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.

Theobroma oil can exist in four different polymorphic forms of which only ____ is stable.
one

Variable stars fall into ____ major physical classifications.
four

Flatworms exhibit ____ forms of life styles, free-living and parasitic.

two