船舶按照技术状况的好坏分类,一般分()类。
A.三
B.四
C.五
D.六
参考答案:B
The student, if well _____ , will pass the examination without much difficulty.
A.preparing
B.prepared
C.to prepare
D.ready
LED色灯机构的正常绝缘电阻应不小于()。
A、20MΩ
B、30MΩ
C、40MΩ
D、50MΩ