--- Could you tell me __________?    

--- Certainly. In half an hour.

A．when will the train to Beijing leave

B．when the train to Beijing would leave

C．when the train to Beijing left

D．when the train to Beijing will leave

下列给药途径中，可产生明显首关消除的是（）.

A、舌下含服

B、静脉注射

C、口服给药

D、吸入给药