外科病人最常发生的缺水是（）

A．原发性缺水

B．继发性缺水

C．等渗性缺水

D．低渗性缺水

E．高渗性缺水

I can still vividly remember to pick our steps in the mountain down the deep valley on my 21 st birthday.()

A. picking.., in the mountains

B. picking ... on the mountain

C. having picked ... from the mountains

D. picking ... from the mountains