单选题Diesel fuel vapors （）.Acan not be ignited by a spark unless the vapor is in a confined spaceBare nontoxic in all concentrationsCcan not be ignited by a spark unless they are at their auto-ignition temperatureDare heavier than air
单选题
Diesel fuel vapors （）.
A
can not be ignited by a spark unless the vapor is in a confined space
B
are nontoxic in all concentrations
C
can not be ignited by a spark unless they are at their auto-ignition temperature
D
are heavier than air
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