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

[Q]: Gravity is the weakest of all _ forces but unlike the others it has an unlimited range.
[A]: four


[Q]: Prolactin exists in _ heterogenic forms which possess varying biological activity.
[A]: three


[Q]: Most roots require from _ to six weeks to dry sufficiently to be safe.
[A]:
three