状语

Millions of people travel about the country by rail， by bus，orby automobile，ordrive to and from their places of work and their homes。

三个by， by， by作为travel方式状语。

The syntactic evolvement of the verb "de" has gone through a lot of stages from a core verb to an inapprehensible element in the word.

单音动词“得”句法演变经历了核心动词到次要动词、状语和补语、结构助词,再到词内不可分析成分这样一个发展过程。