The bus runs past the building once every five minutes ______ the average.
问题描述：
The bus runs past the building once every five minutes ______ the average.
The bus runs past the building once every five minutes ______ the average
选项:
a、above
b、 below
c、 on
d、 at
答
c、 on
on the average
词组
平均,没有问题.