下列中科学的喝水方法是（）。
A、清晨空腹喝一杯凉开水
B、每天只饮用纯净水
C、饥渴时多饮水
D、边吃饭边饮用大量的水
参考答案：A
Having finished his morning work, the manager stood up behind his chair, _______ himself.
A．practising
B．spreading
C．stretching
D．extending
上消化道出血时产生黑粪是由于每日出血量超过（）
A.50ml
B.20ml
C.40ml
D.30ml
E.100ml
