He __________ well in the exam last week, so he __________ hard now.

A. did, studied    

B. didn't, is studying   

C. didn't do, is studying

D didn't, studying   

从事疏浚作业的船舶操纵能力受到限制，夜间在航不对水移动时应显示：（）

A.红、白、红垂直三盏环照灯

B.在任何时候均应显示垂直两盏环照绿灯和垂直两盏环照红灯

C.桅灯、舷灯和尾灯

D.桅灯、舷灯和尾灯，红、白、红垂直三盏环照灯