分类：教育/科学-外语学习
问题：英译汉一句.wherearailwaycrossesanavig 
where a railway crses a navigable water way, and it is impossible to lift the line  high enough for vessels to pass underneath without interception, a bridge must be built which is capable of being opened in order to allow the river or canal traffic to pass.
回答：当铁路穿越需通航的水路,无法用抬高铁路路线的方法使船舶从下面通过,避开交叉时,必须修建一座桥梁,桥可以打开,以使江河或者运河上的船只通过.