信用证上若未注明汇票的付款人，根据《UCP500》，汇票的付款人应是( )。
A．开证人
B．开证行
C．议付行
D．出口人
参考答案：B
简述心脏病肺水肿病人的急救处理。
When people move to another country, they often try _____ the customs of their native land. [ ]
A. to keep on
B. to keep off
C. to keep up
D. keeping up
