英语中两个句子用逗号连接

英语中两个句子用逗号连接
71.\x05________ in the United States,St.Louis has now become the 24th largest city.
A.Being the fourth biggest city
B.It was once the fourth biggest city
C.Once the fourth biggest city
D.The fourth biggest city it was
为什么 逗号怎么能连接两个句子
59.\x05If the building project ________ by the end of this month is delayed,the construction company will be fined.
A.being completed
B.is completed
C.to be completed
D.completed
为什么 怎可以出现两个谓语