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

Q: Most amphibians reach maturity at three or _ years.

A: four
****
Q: Reverse osmosis uses three to ten gallons of water to produce _ gallon of drinking water.

A: one
****
Q: Fallow deer fall into _ main color classifications, white, chocolate and spotted.

A:
three
****