对地方行政建制和行政划分等级划分以及同是城市建制的行政等级划分正确的一项是( )。

A．省级、地级、县级和乡级、村级

B．省级、地级、县级和乡级

C．同是城市建制，其行政等级有省级(直辖市)、地级和县级、乡级

D．同是城市建制，其行政等级有省级、县级、乡级

Only when ______ the data again ______ that there was a mistake. [ ]

A. they had studied; did they realize

B. they had studied; realized they

C. had they studied; did they realize

D. had they studied; realized they