travelling by train is more comfortable than by air 这句话谁是主语?谓语宾语?

问题描述:

travelling by train is more comfortable than by air 这句话谁是主语?谓语宾语?

travelling by train是主语
is 是系动词
more comfortable than by air 是表语
这句话不是主谓宾,是主系表结构