In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[Q]: Carbon comes in _ kinds- dust, coconut shell or granulated.
[A]: three


[Q]: Rheas are brownish instead of black like the ostrich and have _ toes instead of two.
[A]: three


[Q]: Sociobiology is the historical outgrowth of _ prerequisite trends.
[A]:
three