1. Which of the following statement

1. Which of the following statement is not true? A. Ignition energy of combustible vapors is small. B. Combustible gases are easily burned. C. Petroleum vapor can be initiated when the concentration of the vapor in air is between LFL and UFL. D. There is a wide range of upper and lower explosive limits of crude oil.2. The flammable range of hydrogen gas is larger than that of petroleum vapor according to this paragraph, it means _______. A. hydrogen gas is easier to burn B. petroleum vapor is easier to ignite C. hydrogen gas is more dangerous D. petroleum vapor is more dangerous3. The phrase “the correct proportion with air” means _______. A. only when the concentration of the mixture is lower than LFL, an explosion occurs B. only when the concentration of the mixture is higher than UFL, an explosion occurs C. only when the concentration of the mixture is within the limits, an explosion occurs D. only when the combustible gases are in air, an explosion occurs4. The cause of combustible gas explosion is ________. A. they bum in an open vessel B. they bum rapidly in an closed vessel C. they bum due to too much oxygen D. they burn due to lack of oxygen