Ethylene oxide has a lower explosive limit of 2.0% and an upper explosive limit of 100% by volume in air. This means __________.

Correct Answer: Option B — there is no possible ethylene oxide concentration in air which is too rich to burn

The upper explosive limit (UEL) represents the maximum concentration of vapor in air that can support combustion. Since ethylene oxide has a UEL of 100%, it can burn even in the absence of air, meaning there is no concentration of the vapor that is too rich to support a reaction.