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

[EX Q]: Mammals have _ types of cartilage.
[EX A]: three

[EX Q]: Professional chefs use _ tools to keep knives sharp.
[EX A]: two

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