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

[Q]: Every drug has _ names, a chemical name, a brand name, and an official name.
[A]: three


[Q]: Bifocal lenses have _ distinct segments with different powers.
[A]: two


[Q]: Most people require roughly seven to _ hours of sleep a night to stay alert through the day.
[A]:
eight