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

[EX Q]: Epilepsy is defined as having _ or more unprovoked seizures.
[EX A]: two

[EX Q]: Aspiny neurons are of _ sizes.
[EX A]: two

[EX Q]: Willow flycatchers have a lifespan of three to _ years.
[EX A]:
four