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

[EX Q]: Urushiol oil can be active on any surface for _ years and possibly longer.
[EX A]: five

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

[EX Q]: Most people believe that there are _ kinds of taste - salt, sour, bitter, and sweet.
[EX A]:
four