下列哪种心脏病常无震颤
A．室间隔缺损
B．主动脉瓣关闭不全
C．肺动脉瓣狭窄
D．主动脉瓣狭窄
E．动脉导管未闭
参考答案：B
从一个10边形的一个顶点出发，连接其余各顶点，可以将这个边形分割成______个三角形．
More than one worker _____ dismissed. [ ]
a. have been
b. are
c. has been
d. has
