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]: Most amphibians reach maturity at three or _ years.
[EX A]: four

[EX Q]: Sea lions walk on all _ flippers.
[EX A]:
four