答：该问题主要涉及的知识点为：quantity 与后面谓语动词单、复数搭配(即主谓一致).但是关于quantity 与谓语单复数搭配,现在说法不统一.主要有两种观点：
1、与词形保持一致
a quantity of /quantities of 不管后面接复数还是单数(包括不可数)名词,只看quantity 本身.即：a quantity of 中的quantity 是单数,谓语动词就用单数；quantities of 中quantities 是复数,谓语动词则与复数保持一致.例如：
Quantities of nuts were on the table.
A quantity of nuts was on the table.
2、与意义保持一致
这种观点认为,不应该看a quantity of / quantities of 本身,而应该看这个词组后面所接的是什么名词,如果后面的名词是单数(或不可数),则谓语用单数；如果名词是复数,那么谓语用复数.这一点与a lot of 相同,即遵循意义一致原则.例如：
There is only a small quantity of wine left.
Great quantities of sand was washed down the hillside by the rain last night.
A large quantity of air conditions have been sold since the summer came.
Huge quantities of oil were shipped to Japan last year.
结论：目前,比较倾向于与quantity 的词形保持一致,即 a quantity of 是单数,quantities of 是复数,而不管后面接单数或复数的名词,如果是这样的话,这个短语后面用复数.
例如,某省一道高考题如下：
With many forests being destroyed, huge quantities of good earth ______ each year.
A. is washing away B. is being washed away
C. are washing away D. are being washed away
它所给的答案是D. 此题中,earth 是不可数名词,但quantities 是复数,所以谓语采用了复数形式D.
还有,这个选择题：
It's a pity that large quantities of wood ____that way all over the world.
has been wasted 还是have been wasted,还是 has wasted ,have wasted
用have been wasted,分析：quantities是复数形式,所以have,wood 是被浪费的,要用被动语态.