来自陈挚睿的问题
_________intheUnitedStates,St.Louishasnowbecomethe24thlargestcity.A.ThefourthbiggestcityitwasB.OncethefourthbiggestcityC.BeingthefourthbiggestcityD.Itwasoncethefourthbiggestcity应该选哪个呢?有什么不同吗?请
_________intheUnitedStates,St.Louishasnowbecomethe24thlargestcity.
A.ThefourthbiggestcityitwasB.Oncethefourthbiggestcity
C.BeingthefourthbiggestcityD.Itwasoncethefourthbiggestcity
应该选哪个呢?有什么不同吗?请分析一下句子成分（即所填空中的句子应作什么成分）.
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