单项选择题
A.checking the loading sheet
B.loading to within 1 percent of outage
C.loading to within 10 percent of the safety relief valve setting
D.filling to the maximum level indicated on the liquid level gaging device
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（）.
单项选择题 Storage batteries should be charged in a well ventilated area because（）.
单项选择题 One of the principal dangers inherent in liquefied petroleum gas is（）.