鲫鱼不断地用口吞水、由鳃排水的作用是 [ ]
A．完成食物消化
B．完成运动作用
C．完成呼吸作用
D．调节体内外水分平衡
答案：C
-Mum, I am feeling tired and sleepy now.
-You so late last night. [ ]
A. couldn’t have stayed up
B. mustn’t have stayed up
C. shouldn’t have stayed up
D. needn’t have stayed up
建筑材料发展方向应逐渐由天然材料转变为人造材料。( )
