有机物CH₂＝CHCH₂CH₂Br分别与下列物质反应：①H₂O/H^＋，②HBr，③NaOH浓溶液，加热，④NaOH乙醇溶液，加热。其中产物只含有一种官能团的反应是

A．②④

B．②③

C．①③

D．①④

Could you tell me ________ last night?[ ]

A.what you were doing                  

B.what were you doing

C.what you are doing                  

D.what are you doing