已知关于x的一元二次方程mx2-10x+5=0有实数根，则m的取值范围是______．
由题意知，m≠0，△=100-20m≥0，
∴m≤5且m≠0．
We had better hurry.Our teacher us.
A．wait for
B．must wait for
C．must be waiting for
D．has waited for
带电作业时风力大于（）级，不宜带电作业。
A.5
B.6
C.4
