单项选择题

基础知识,章节练习,土木工程师（水利水电）现代技术基础,电气技术基础

A.垂直向下
B.垂直向上
C.左上方
D.右上方
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单项选择题
If an electric cargo winch is being used to lift a draft of cargo and the engine room loses all power，which will occur ________．A.A pawl，forced by a spring mechanism，will engage the teeth of the bull gear and hold the loadB.An electromagnetic brake will hold the load where it is suspendedC.The load will fall rapidly to the deck unless the foot brake is engagedD.The load will slowly lower to the deck under control of the drag of the winch motor
A.A.A
B.An
C.The
D.The
单项选择题
河、沟、渠是农田生态工程的重要组成部分，起输送水的作用。（ ）
A．对
B．错
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