现代风格大理石电视墙:There are trees on either side of the road.此句中either可以换成each吗？

There are a lot of trees on "either" side of the road? There are many trees planted 对吗 There are ( )trees in the park There are trees on either side of the road.此句中either可以换成each吗？ How many trees are there on top of the mountain?这里的on top of 为什么不是on the top of 呢？ On___side of the road there are many trees. There are two (s )on this letter. There are many boats on the lake . there are a lot od beautiful trees on___this side of the road ___ the other 有这样一句话:There are twenty more trees to be planted.那么这一句呢: