TASK DEFINITION: In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
PROBLEM: Reverse osmosis uses three to ten gallons of water to produce _ gallon of drinking water.

SOLUTION: one

PROBLEM: Carbon dioxide accounts for _ fourths of the predicted increase in the greenhouse effect.

SOLUTION: three

PROBLEM: Manatees swim _ to six miles per hour.

SOLUTION:
two