a number of foreigners visited our school yesterday中为什么用a number of为什么不用the number of?

the number of,a small number of,a number of. a number of the number of a growing number of a.number.of?用法 a small number of a number of 造句 a number of同义词 After a number of a number of a lager number of the number of、a number of、large number的区别 a little number of a small number of什么区别 a number of students还是a number of the students A number of的用法 A number of 的用法 a number of +可数/不可数? a large number of 同义词 a number of the students