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

[EX Q]: White sturgeon inhabit _ large river systems, all on the western coast of North America.
[EX A]: three

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

[EX Q]: Sloth mothers give birth to _ baby once a year, after a six month pregnancy.
[EX A]:
one