Last year the number of students who graduated with a driving license reached 200,000, a(n) of 40,000 per year. A. average B. number C. amount D. quantity 答案:A a number of 许多 amount of 一般加不可数名词表金额, a quantity of 既可以加可数也可以加不可数,但没有平均每年增加的意思。 已知方程x2+kx﹣12=0的一个根为2,求k的值及方程的另外一个根?