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]: Biological islands are of ____ general types, geographical and ecological.
[A]: two


[Q]: Humans have two lungs, each fed by ____ bronchus.
[A]: one


[Q]: G proteins consist of ____ subunits called alpha, beta and gamma.
[A]:
three