题目内容
(请给出正确答案)
[单选题]
我国煤尘爆炸的上下限是()。
A.下限45mg/m3,上限2000mg/ m3
B.下限45g/ m3,上限2000g/ m3
C.下限45mg/cm3,上限2000mg/cm3
D.下限45m/m m3,上限2000mg/mm3
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A.下限45mg/m3,上限2000mg/ m3
B.下限45g/ m3,上限2000g/ m3
C.下限45mg/cm3,上限2000mg/cm3
D.下限45m/m m3,上限2000mg/mm3
A.组中值=(上限+下限)÷2
B.组中值=上限+下限÷27
C.组中值=上限÷2+下限
D.组中值=下限+(上限-下限)÷2
E.组中值=上限-(上限-下限)÷2
A.组中值=(上限+下限)÷2
B.组中值=上限+下限÷2
C.组中值=上限÷2+下限
D.组中值=下限+(上限一下限)÷2
E.组中值=上限一(上限一下限)÷2
A.下限≤50x109/L;上限>200x109/
B.下限≤55x109/L;上限>200x109/L
C.下限≤30x109/L;上限>200x109/L
D.下限≤50x109/L;上限>180x109/L