单项选择题
According to the Chemical Data Guide，when burning，the grade B flammable liquid，carbon disulfide produces（）.
A.phosgene gas B.sulfuric acid gas C.sulfur dioxide gas D.carbon tetrachloride
单项选择题 According to regulations，a cargo hose used for transferring liquefied gases must have a bursting pressure of（）.
单项选择题 A vessel behaves as if all of its weight is acting downward through the center of gravity，and all its support is acting upward through the（）.
单项选择题 A spark arrestor（）.
