This is the longest train that i have ever seen.为什么引导词不能用which用that读的是顺一些,可是为神什么不能用which?不是都指物吗?

this is the longest rail line network in the world改写this is the longest rail line network this is the longest rail line network in the world 改为同义句this is the longest rail line network （）（）（）（） this is the longest bridge that i have everthis is the longest bridge （ ）i have ever seen.A 、who B 、that C 、which D 、A and B This is the longest train that i have ever seen的意思 This mountain is the__one in the area.A.highest B.tallest.Cdeepest D.longest the great wall is the to longest 是is the to.还是is the longest. what is the longest word in English which is the longest word in english Which is the longest English word? What is the longest river in Chain? Which is the longest river?怎么回答 Which is the longest river in England? what is the longest river in Europe? what is the longest letter which letter is vegetawhat is the longest letterwhich letter is vegetable This river is the longest in the whoie country.保持原意.This river is longer than__ __in the whole country.空格是三个。呵呵。不好意思！ This is ___the other threeA.longer than B.longest of C.longest in D.longer of 1、This is the longest word in English.的中文意思 2、It has only six letters.的同义句 This cloth is the same __as that one.A.long B.length C.longer D.longest.应该选哪一个,为什么?