Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Romantic love involves ____ people.
two

Some people routinely sleep only ____ hours a night but feel fine during the day.
four

Ungulates are hoofed mammals from ____ orders, artiodactyla and perissodactyla.

two