第6课

　　关于逗号的一些知识
　　原则：逗号没有能力连接两个单独的句子。
　　如何区分短语与句子？一个结构如果有完整的谓语部分就是句子。
　　何为完整的谓语部分？如果能判断出一个结构的时态就可以称这个结构为完整的谓语部分。
　　在什么样的情况下一个逗号可以将句子分成两部分，而这两部分都有完整的谓语呢？
　　1 两个句子中间有连接词连接；
　　2 这两个句子是主从句关系（主从句之间一定要有句子引导词来引导）。
　　10. Walter offered us a lift when he wasleaving the office, but our work _A_, we declined the offer. [declined v. 婉言谢绝]
　　A not being finished B not having finished
　　C had not been finished D was not finished
　　42. A survey was carrie3d out on the deathrate of new-born babies in that region, _D_ were surprising. [survey 调查]
　　A as results B which results C the results of it D the results of which
　　51. All flights _D_ because of thesnowstorm, many passengers could no nothing but take the train. [having beencanceled这里是独立主格作原因状语]
　　A had been canceled B have been canceled
　　C were canceled D having been canceled