Which form of sterilization uses ethylene oxide gas?

The correct choice relates to a sterilization method that utilizes ethylene oxide gas, which is specifically tied to chemical vapor sterilization. Ethylene oxide is a highly effective agent for sterilization, particularly for heat-sensitive instruments and materials that cannot withstand the high temperatures involved in steam sterilization or dry heat sterilization.

Chemical vapor sterilization employs a combination of chemicals, including formaldehyde and other gases, to create a vapor that envelops the instruments, killing microorganisms. Ethylene oxide's low temperature operation makes it an ideal choice for delicate equipment, ensuring sterilization without causing damage.

The other forms of sterilization mentioned—steam, dry heat, and radiation—do not involve ethylene oxide gas. Steam sterilization typically uses saturated steam under pressure, dry heat relies on hot air to sterilize, and radiation sterilization involves the use of ionizing radiation. Therefore, understanding the specific mechanisms and appropriate applications of each form of sterilization clarifies why chemical vapor sterilization is the correct choice for this question.