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.

[Q]: Dogs are pack animals, and ____ dogs is the minimum number for proper socialization.
[A]: five


[Q]: Most orthoptists work ____ hours a day, four or five days a week.
[A]: eight


[Q]: Scientists say that earthly life has been around nearly ____ billion years.
[A]:
four