停车检修容器可燃气体含量不得大于（）才能动火检修。
A.3％
B.1％
C.0.5％
D.0.2％
参考答案：D
区域联防的防守原则是什么？
Damage to cargo caused by dust is known as（）.
A.contamination
B.oxidation
C.tainting
D.vaporization
