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

[Q]: Plasma levels fall by about a half within three to _ hours.
[A]: four


[Q]: Birds bitten by infected mosquitoes are infectious from _ to eight days.
[A]: four


[Q]: Intertidal areas show a lack of large clams, resulting in a low average size for all _ species.
[A]:
four