单项选择题
Fires occurring in combustible metals, such as sodium or magnesium, are classified as a （）.
A.class A B.class B C.class C D.class D
单项选择题 A tank which has been sealed for a long period of time can be dangerous because （）.
单项选择题 Records of garbage disposal are required to be maintained （）.
单项选择题 The use of sinking and dispersing agents for the removal of surface oil is （）.
