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

[Q]: Atoms are most stable when they have _ electrons in their outer electron energy level.
[A]: eight

[Q]: Flatworms exhibit _ forms of life styles, free-living and parasitic.
[A]: two

[Q]: Shoes typically lose their cushioning after three to _ months of regular use.
[A]:
six