﹣1﹣1=____ .
在测定“小灯泡电功率”的实验中,电源电压为4.5V,小灯泡额定电压为2.5V、电阻约为10Ω.
Jane got up late this morning,so she had to take a ____ to school.
下面图形(单位:厘米)的面积是____