工业三废通常是指废水、废气、废料。( )
参考答案：错
关于x的一元二次方程x2+mx+9=0有两个相等的实数根，则m的值是（ ▲ ）
A．3或-3
B．6
C．-6
D．6或-6
— __________?
— She is a nurse.
[ ]
A. Where does your mother do
B. What does your mother do
C. What is your mother doing
D. Who is your mother
