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

[Q]: Most intestinal worms take _ to four weeks for maturation from their larval stages into adults.
[A]: three


[Q]: Stroke is our nation's number _ killer, and a leading cause of disability for older adults.
[A]: three


[Q]: Some babies sleep through by age _ weeks.
[A]:
six