变压器有载调压切换装置在极限位置时，其机械联锁与（）的电气联锁动作应正确。
参考答案：极限开关
I have bought two pens, ____ write well.
A．none of which
B．neither of which
C．both of which
D．all of which
有实地范围相同的某城市规划图的两幅地图中，甲图比例尺为乙图的2倍，则甲图幅为乙图的（）
A.1/4倍
B.1/2倍
C.2倍
D.4倍
