动脉导管未闭患儿的周围血管征包括（）。
A.水冲脉
B.毛细血管搏动
C.青紫
D.股动脉枪击音
E.声音嘶哑
参考答案：A, B, D
求通过原点且与两直线l1:x+2y－9=0,l2:2x－y+2=0相切的圆的 方程.
--- The weather isn’t good enough for an outing, is it?
---Not in the least. We can’t have ______ at this time of the year.[ ]
A. a worse day
B. a nice day
C. such bad a day
D. so fine day
