单选题 For hot operation in the no-fire zone, the distance between the oxygen cylinder and the acetylene cylinder is at least ( ) meters.

单选题 A gas explosiometer measures the ( ) of combustible gases.

单选题 When doing hot fire analysis, the interval between sampling and hot fire is more than ( ) minutes, or the stop time in the middle of hot work is more than ( ) minutes, you must resamb for analysis.

单选题 High work means work performed above the fall height datum ( ) (inclusive), where there is a possibility of falling.

单选题 When the height of the high work is ( ) m, it is called the level 2 high work.

单选题 For ( ) (including) above high work, the "high work permit" should be applied.

单选题 ( ) Does not fall under fall protection.

单选题 When the chemical equipment is hot repair, the medium that can not be directly used to replace the combustible gas is ( ).