【单选题】【消耗次数：1】
当氧含量低于( )%时，煤尘就不再爆炸
①
A.21
②
B.20
③
C.17
④
D.14
参考答案：
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相关题目
【单选题】
<img src=https://huaweicloudobs.ahjxjy.cn/6F21E9751517D743ADC53B4C538D1F23.jpg title=14-A.jpg alt=14-A.jpg/>
①
<img src=https://huaweicloudobs.ahjxjy.cn/8910741CBF142F9D5F2BE16ED3FAF872.jpg title=14-1.jpg alt=14-1.jpg/>
②
<img src=https://huaweicloudobs.ahjxjy.cn/8C7610FCB8AAC03143DE3E8D7AF89734.jpg title=14-2.jpg alt=14-2.jpg/>
③
<img src=https://huaweicloudobs.ahjxjy.cn/6762E59594E21216289DDB3EA976F4C8.jpg title=14-3.jpg alt=14-3.jpg/>
④
<img src=https://huaweicloudobs.ahjxjy.cn/ED2AAD092FF1F39A0A35736EA5EC43D4.jpg title=14-4.jpg alt=14-4.jpg/>
随机题目
【单选题】
水准测量中，设后视尺A的读数为a=2.713m，前视尺B的读数为b=1.401m，已知A点高程为15.000m，则水准仪视线高程为（）m
①
13.688
②
16.312
③
16.401
④
17.713
【单选题】
某导线全长620m，纵横坐标增量闭合差分别为<img width="162" height="19" src="data:image/png;base64,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"/>，则导线全长相对闭合差为（ ）
①
1/2200
②
1/3100
③
1/4500
④
1/15500
【单选题】
沉降观测时水准基点和观测点之间的距离一般应在米范围内，一般沉降点是均匀布置的，距离一般为米。
①
A、80、5~10
②
B、80、10~20
③
C、100、5~10
④
D、100、10~20