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

[Q]: Young groundhogs are weaned and ready to seek their own dens at _ to six weeks of age.
[A]: five

[Q]: Knives have _ cutting edges for double cutting life.
[A]: two

[Q]: Earthquakes produce _ different types of seismic waves.
[A]:
three