a

a quantity of+可数名词复数、谓语动词用复数；a quantity of+不可数名词、谓语动词用单数。即修饰可数或不可数名词均可，作主语时采取就近一致的原则，其谓语动词通常与短语中of后面的名词的数保持一致。

a quantity of谓语用单数还是复数

a quantity of+可数名词复数、谓语动词用复数；a quantity of+不可数名词、谓语动词用单数。

若单独用quantity作主语，谓语动词用单数。

如：It is used to emphasize that the quantity is very large。

它用于强调数量很大。若该结构变成(large)quantities of…这样的形式，则当它用作主语时，其谓语动词一律用复数。

如：Huge quantities of oil were spilling into the sea。大量的石油渗到海里。

quantities of和a quantity of的区别

quantities of和a quantity of都可以修饰可数名词和不可数名词，区别在于：

quantities of在修饰不可数名词，并且和后面的名词一起做主语时，谓语由它决定，也就是用复数。

a quantity of修饰不可数名词，并且和名词一起做主语时，谓语动词由后面的名词决定，也就是用单数。

例如：Quantities of energy are saved today. (今天大量的能源被节约)

A quantities of energy are saved today.

Quantities of cash have been withdrawn from the bank.

(大量的现金已经被从银行取出)

Aquantity of ready-use 35 mm ammunition in clips is also carried.

一批准备使用35毫米弹药在剪辑，也获得通过。

其他时候俩者可互换。

The milk carton, in turn, has a quantity of milk inside it.

=The milk carton, in turn, has quantities‍ of milk inside it

这盒牛奶，再进一步，它里面牛奶有一个量。