Final answer:
Mixing ethylene oxide (EO) with helium minimizes the risk of fire as helium is an inert, non-flammable gas that does not support combustion. Helium is safer to use in various applications due to its non-reactive properties and does not cause narcotic effects under high pressures like nitrogen.
Step-by-step explanation:
The risk of fire with EO, which is presumably ethylene oxide, can be minimized by mixing with a substance that is non-flammable and does not support combustion. In this context, the best option for mixing is helium. Helium is a noble gas that is inert, meaning it does not react easily with other substances, including oxygen. It is commonly used in applications such as filling balloons and airships because it is non-flammable, making it safer than hydrogen.
Moreover, helium is also used in diving to form a mixture with oxygen because, unlike nitrogen, it does not cause narcotic effects under high pressures. This mixture helps avoid nitrogen narcosis, also known as 'rapture of the deep.' Additionally, helium provides an inert atmosphere necessary for chemical processes, melting, and welding easily oxidizable metals. Therefore, when considering the risk of fire, mixing EO with helium would minimize that risk, making option (d) the correct answer to this multiple-choice question.