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

[EX Q]: Most people see the world through _ types of visual-receptor cells.
[EX A]: four

[EX Q]: Carbon dioxide accounts for _ fourths of the predicted increase in the greenhouse effect.
[EX A]: three

[EX Q]: Some women describe their symptoms as feeling about _ months pregnant.
[EX A]:
four