an important factor in a market-oritned economy (主语） / is （谓语） / the mechanism （宾语）,后面是宾补吧
by which (这里的which 指代 the mechanism)
consumer demands can be expressed and responded to by producers
expressed 和 responded to by producers
不好意思,我不知到这些语法术语,但是这样理解是没错的.