a mass of =masses of 大量的.其后接可数名词和不可数名词均可.由
它构成的词组作主语时,谓语动词的数取决于 mass 或 masses.例如：
①There are masses of ice in the river.河里有很多冰.
② There is a mass of children in the yard.院子里有很多孩子.
③I've a mass of things to do this morning.今天上午我要处理很多事.
④There are masses of people in the hall.大厅里有很多人.