There are so many tall buildings on--sides of the street.选什么

There are so many tall buildings on__sides of the street.选什么呢?
这是一道单项选择题
There are so many tall buildings on__sides of the street.
4个选项分别是
A.both B.each C.all D.every
麻烦帮助我选出适合的答案,并请说得详细一些.