水下混凝土的浇筑速度有何要求？
参考答案：水下混凝土每小时的浇筑数量，应使每根导管均有适当的埋入深度，且不宜小于0.25m。
— A medical team was sent to Japan by air five hours ago.
— So they ________ have arrived by now.The flight usually takes four hours or so.[ ]
A. might
B. could
C. must
D. need
血液中LDL的主要功能是转运（）
A.胆固醇
B.外源性TG
C.内源性TG
D.磷脂
E.糖脂
