桔梗对心血管系统的作用是（）
A.收缩血管
B.升高血压
C.兴奋心脏
D.扩张血管
E.心率加快
参考答案：D
Being hard-working is of the highest __________ to becoming successful.
A．important
B．to be important
C．importance
D．being importance
“ZRN”键是使数控系统处于( )状态
A．自动
B．编辑
C．空运转
D．回零
