进入落地式配电箱的电线保护管，管口宜高出配电箱基础面（）
A.30mm
B.40～60mm
C.50～80mm
D.1.5m以上
参考答案：C
To show our respect, we usually take our gloves off _______ we are to shake hands with.
A．whoever
B．whenever
C．whichever
D．wherever
发f音时、与上前牙切缘接触的是（）
A.下前牙切缘
B.舌尖
C.下唇
D.A+B
E.B+C
