Tai'an is very beautiful,There are many trees on ___ side of the roads.A each B every C both D all

选on each side of ... 每一边......
否则on both sides of ...两边都......
all sides 指的是有许多条边的物体。

every 既考虑单个，又考虑整体。 Every student in our class likes the teacher. 每个学生（所有）学生都喜欢......。

each则只考虑单个。 Each student has a pencil case. 每个人都有铅笔盒。（没有‘都’的意思）

each

both两边，后用sides
every每一边
all sides所有边

c

each，every 是每个
both是两个都
all是所有都
道路只有两面，故c