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

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

[EX Q]: Females inherit _ X chromosomes, one from each parent.
[EX A]: two

[EX Q]: Spiders have eight legs but ants, bees, beetles and other insects have only _ legs.
[EX A]:
six