If you do things ________, usually you can't do them well.
A:in a hurry
B:from now on
C:just now
D:at once
学生实验用的电压表,当使用“+”和“15”两个接线柱时,电压表的量程和最小刻度值分别是( )
一元二次方程x2﹣9=0的根是( )