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

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

[EX Q]: Smokers die an average of six to _ years earlier than nonsmokers.
[EX A]: eight

[EX Q]: Most juveniles remain in their natal river from one to _ years before migrating to the ocean.
[EX A]:
six