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

[EX Q]: Females inherit _ X chromosomes, one from each parent.
[EX A]: two

[EX Q]: Aquatic adults have prominent red reathery gills, are large, and have _ toes on each foot.
[EX A]: four

[EX Q]: Hearing is acute by three or _ weeks and kittens learn to determine what sounds mean.
[EX A]:
four