During the pase two years,the ( ) of automobile accidents in london city has deceased.

1,the number of 是固定搭配,后面的动词要用单数形式.这道题用了has .
2,没有the quantity of 的用法,只有
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.