单项选择题
The airborne concentrations of substances (such as H2S) under which nearly all workers may be repeatedly exposed without adverse effects are called（）.
A.exposure limits
B.concentration limits
C.threshold limit values
D.substance limit values
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相关考题
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Storage batteries should be charged in a well ventilated area because（）.
A.they generate heat
B.they emit hydrogen
C.of the toxic fumes they emit
D.they recharge faster in a well ventilated space -
单项选择题
One of the principal dangers inherent in liquefied petroleum gas is（）.
A.as it warms up it becomes heavier than air
B.the way it reacts with sea water
C.the strong odor it produces
D.its low temperature causes frostbite or freezing -
单项选择题
Name one major advantage of transporting gas under refrigeration.（）
A.It increases its volume
B.It reduces its volume
C.It has less product per volume
D.None of the above
