一个角的补角是它的余角的3倍，则这个角是 度；
45
设这个角的度数为x，则180°-x=3（90°-x），解得：x=45°
— There is little water left in the bottle, ______?
— No, we need to buy some more before we run out of it.
A．is there
B．isn’t there
C．is it
D．isn’t it
绘图题：画出某220/380V三相四线制电路供电一路进线，三路出线照明配电的电气主接线。
