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

[Q]: Architectural shingles are twice or _ times as thick as ordinary shingles.
[A]: three

[Q]: Digoxin works in _ ways.
[A]: two

[Q]: Incubation takes about _ weeks, and the owlets fledge after about one month.
[A]:
four