a quantity of +名词作主语，谓语是单数还是复数由其名词是不可数名词单数还是可数名词复数来决定，具体情况归纳如下。
(1) a quantity of +可数名词复数，作主语，谓语用复数
A large quantity of flowers were heaped on the martyr’s tomb.
(2) a quantity of +不可数名词单数，作主语，谓语用单数
A large quantity of beer was consumed. Quantities of food were on the table.
特别备注：
A: a large quantity of +不可数名词，作主语，谓语用单数
船里有大量的鱼肉。
There is a large quantity of fish in the boat.
B: a large quantity of +可数名词复数，作主语，谓语用复数
印刷了大量的书。
Alarge quantity of books were printed.
C: (large) quantities of 可以数名词复数/不可数名词单数，作主语，谓语都用复数
A: quantities of +不可数名词单数
这个镇去年浪费了大量的水。
Quantities of water were wasted in this town last year.
B:quantities of +可数名词复数
就在圣诞节以前还有过许多购买东西的顾客。
There were large quantities of shoppers just before Christmas.
可有的语法书上说a quantity of后不论接什么名词，谓语用单数。quantities of后无论接什么名词，谓语用复数。纠结中。
继续跟踪回答如下：
（特别备注：表示“大量”的有两种形式:a large quantity of和large quantities of。a quantity of接不可数名词时,谓语动词用单数形式,接可数名词复数时,谓语动词用复数形式; quantities of无论是修饰不可数名词,还是可数名词复数,谓语动词都要用复数形式。）
