一等级三角锁的每条锁长为(),是国家平面控制网的骨干。
A.100~150km
B.100~200km
C.150~200km
D.200~250km
参考答案:D
—Do your brother and you look the same?
—No. He's _____ taller than me.[ ]
A. little
B. a little
C. many
两导体间或任一导体与地之间均不得超过的工频电压有效值为()。
A.12V
B.24V
C.36V
D.50V