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

[Q]: Bacteria acquire genes for resistance in _ ways.
[A]: three


[Q]: Economists divide resources into _ basic categories of land, labor, capital, and management.
[A]: four


[Q]: Births usually occur at night, any time of the year and every _ years or so.
[A]:
four