all是不定代词
All of them are student.他们所有人都是学生回.All is going well.一切都很答好.
前者指学生,而且不止一个,要用复数.后者all表示抽象意义,表示所有事情.所以用单数.
不定代词有some(dusomething,somebody,someone),any(anything,anybody,anyone),no(nothing,nobody,no one),every(everything,everybody,everyone),all,each,both,much,many,(a)little,(a)few,other(s),another,none,one,either,neither.