正常状态下，血房水屏障可选择性通过的是（）
A.水
B.蛋白质
C.电解质
D.抗原
E.以上均可以
参考答案：A, C
---I met Daniel in the street yesterday, I ________ him since he left for Beijing.
--- Well, does he look like what he used to be?
A．haven’t seen
B．didn’t see
C．hadn’t seen
D．wouldn’t see
便携式超声诊断仪的国内供电是（）
A.220V，50Hz
B.110V，50H
C.220V，60Hz
D.110V，60Hz
E.360V，50H
