TASK DEFINITION: In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
PROBLEM: Saturated bonds are when each of the carbons has _ single bonds as in the top figure.

SOLUTION: four

PROBLEM: Gravity is the weakest of all _ forces but unlike the others it has an unlimited range.

SOLUTION: four

PROBLEM: Most turbines have either _ or three blades.

SOLUTION:
two