这是我的回答.
从朗文词典中得来的
across
[preposition/adverb] from one side of something to the other
The children ran across the road.
I've always wanted to sail across the Atlantic.
We gazed across the valley.
The traffic was heavy so it took a long time to get across.
across to
He walked across to the window.
over
over
[preposition] going from one side of something to the other,especially by flying,jumping,climbing,or using a bridge
over他更多的用于使用某种方法,工具,还有其习惯用法
A cat jumped over the fence.
the road over the mountains
one of the bridges over the Rhine
所以是over the bridge
