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.

[EX Q]: Mammals have ____ cervical vertebrae, a number that remains remarkably constant.
[EX A]: seven

[EX Q]: Romantic love involves ____ people.
[EX A]: two

[EX Q]: Young horses spend their first ____ or five years with very little contact with humans.
[EX A]:
four