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【多选题】
下列说法错误的是( )。A.
在电梯调试试运行前，绝缘测试，以防各部件与电线间或电线间的短接故障
B.
如果电梯在检修状态下能运行，则说明电梯主拖动控制系统、安全回路、机械系统无故障
C.
短接层门联锁开关后使电梯运行，是电梯维修中经常使用的故障判断方法
D.
层站及层楼指示灯出现故障不影响电梯使用
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皮皮学刷刷变学霸
举一反三
【单选题】集中式船舶空调装置常允许采用一部分回风是因为（）。
A.
乘员对空气新鲜程度要求不高
B.
为满足乘员对空气湿度的严格要求
C.
节约能量是首要的要求
D.
按热平衡求出送风量远大于新鲜空气的需求量
【单选题】---I heard you had left our Disneyland admission coupons at home.
A.
-Yes. But we were lucky not to leave our visas. __________, we would have had to return home.
B.
So
C.
And
D.
However
E.
Otherwise
【简答题】N 型硅,电子迁移率是空穴迁移率的二倍,少子寿命为 1 微秒,温度 300K 时热平衡电子浓度为 10 15 cm -3 。现用光照射该样品,光被半导体均匀吸收,电子和空穴对的产生率是 10 20 cm -3 ·s -1 ,试计算 : 1. 光照产生的非平衡载流子浓度 2. 电子和空穴的准费米能级 3. 光照前后电导率的变化率 4. 光照突然停止 1 微秒后,半导体中非平衡载流子浓度
【单选题】—Are you here on business? —No, .This is my holiday.
A.
with pleasure
B.
a pleasure
C.
for pleasure
D.
It’s my pleasure
【单选题】---I heard you had left our Disneyland admission coupons at home.
A.
-Yes. But we were lucky not to leave our visas. __________, we would have had to return home.
B.
Otherwise
C.
And
D.
However
E.
So
【单选题】— Hey, I heard you had left the company. Why did you do that? — _____________ I resigned was the company never kept its promises.
A.
Because
B.
As
C.
Since
D.
The reason that
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