先天性心脏病动脉导管未闭可见（）。
A.水冲脉
B.脱落脉
C.无脉
D.交替脉
E.奇脉
参考答案：A
构件承受轴向压力后，抗剪承载力会提高。( )
______ Jason is willing to help, he doesn't have much time available. [ ]
A. As
B. Since
C. While
D. Unless
