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


[Q]: Cichlids are popular in the aquarium hobby for a ____ reason.
[A]: four


[Q]: All pollen grains develop initially in groups of ____ called tetrads.
[A]:
four