Amixture above the upper flammable limit is too rich to burn or explode. a vapor/air mixture below the lower flammable limit is too burn or explode. a. combustible b. lean c. rich

The answer is B: Lean.

Before an explosion can occur, certain conditions must be met. These conditions include combustible gas like fuel, air in certain proportions, and a spark or a flame. The minimum or least concentration of a particular combustible vapor or gas that will burn in air is defined as the LEL (Lower Explosive Limit) for that gas. Below this level, the mixture becomes very lean to burn. On the other hand, the maximum concentration is defined as the UEL (Upper Explosive Limit). Above this level, the mixture is too rich to burn

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