下列不属于沟通通道障碍的是( )。
A．外部干扰 B．沟通渠道过长C．沟通渠道较少 D．选择沟通媒介不当
参考答案：C
如果方程x2-2x+m=0的两实根为a，b，且a，b，1可以作为一个三角形的三边之长，求实数m的取值范围．
Unemployment provides a chance for you to rethink ______
A．what you find and how to keep it
B．what you want and how to get it
C．how best you can do the new job
D．how best you can sort out a new job
