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The correct response is that a mixture of 12% gas and 88% air will not burn. This conclusion is reached based on the concept of flammability limits. For a gas to ignite and sustain a flame, it needs to be present in a specific concentration range when mixed with air. Commonly known as the lower and upper explosive limits, these ranges define the minimum and maximum concentrations of gas in air that are needed for combustion to occur.

In the case of many hydrocarbon gases, the lower explosive limit is typically higher than 12%. For instance, if the lower explosive limit is around 5% for a certain gas, then a mixture containing only 12% gas does exceed this limit. However, without hitting the correct concentration and with the presence of excess air, it will not ignite or sustain a flame under standard conditions.

Therefore, a mixture of 12% gas and 88% air will not initiate combustion, making it non-flammable in such a concentration.