a mass of/masses of,an amount of/amounts of,a good supply of/ supplies of,an abundance of加名词时谓语动词的选择由量词的单复数决定.其中amount只修饰不可数名词,mass,supply,abundance可数和不可数名词均可修饰.
例如：There is a mass of boys in the yard.
There are masses of ice in the river.
这体现的主谓一致原则中的语法一致:谓语动词单复数完全由主语决定