Explosion limit is one of the main parameters to evaluate the fire risk of combustible gas, liquid vapor, dust and other substances. Therefore, A is correct.

The high concentration that can cause explosion is called that upper limit of explosion. Therefore, B is correct.

(2) Initial pressure. When the initial pressure of combustible mixed gas increases, the explosion range increases and the explosion risk increases. It is worth noting that the initial pressure of dry carbon monoxide and air mixed gas increases, and its explosion limit range narrows; So, C is wrong.

(3) Initial temperature. The higher the initial temperature of mixed gas, the larger the explosion limit range of mixed gas and the greater the explosion risk; Therefore, d is correct.

Generally, the explosion limit in oxygen is greater than that in air; So e is wrong.