48. _C_ one time， Manchester was the home of the most productive cotton mills in the world. [at one time 曾經，一度]

　　A On B By C At D Of

　　49. _A_ it or not， his discovery has created a stir in scientific circles.

　　A Believe B To believe C Believing D Believed

　　believe it or not 信不信由你。 creat a stir 引起轟動。

　　50. Mr. Morgan can be very sad _C_， though in public he is extremely cheerful.

　　A by himself B in person C in private D as individual

　　in public 在公眾面前; in private 私下單獨一個人的時候。

　　第6課

　　關于逗號的一些知識

　　原則：逗號沒有能力連接兩個單獨的句子。

　　如何區分短語與句子?一個結構如果有完整的謂語部分就是句子。

　　何為完整的謂語部分?如果能判斷出一個結構的時態就可以稱這個結構為完整的謂語部分。

　　在什么樣的情況下一個逗號可以將句子分成兩部分，而這兩部分都有完整的謂語呢?

　　1 兩個句子中間有連接詞連接;

　　2 這兩個句子是主從句關系(主從句之間一定要有句子引導詞來引導)。

　　10. Walter offered us a lift when he was leaving the office， but our work _A_， we declined the offer. [declined v. 婉言謝絕]

　　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 death rate of new-born babies in that region， _D_ were surprising. [survey 調查]

　　A as results B which results C the results of it D the results of which

　　51. All flights _D_ because of the snowstorm， many passengers could no nothing but take the train. [having been canceled 這里是獨立主格作原因狀語]

　　A had been canceled B have been canceled

　　C were canceled D having been canceled