Last year the number of studects who graduated with a driving licence reached 200 000 a(n

问题补充：

Last year the number of studects who graduated with a driving licence reached 200,000, a(n) of 40,000 per year.

A. average

B. number

C. amount

D. quantity

答案：

(答案→)A. average

B. number

C. amount

D. quantity

解析：an average of平均 a numberof 很多an amount of 数量（修饰不可数名词）

a quantity of很多，句意“去年考取驾照的学生数达到200000平均每年40000”，答案A。