Final answer:
The gas that has a germicidal, healing, and drying effect on the skin is ozone gas (b). Ozone is an effective germicide and is formed from oxygen under certain conditions. Although hydrogen peroxide is also used as a skin antiseptic and disinfectant, it can damage skin tissue with repeated applications.
Step-by-step explanation:
The gas generated close to the skin's surface that has a germicidal, healing, and drying effect is ozone gas (b). Ozone (O3) is an allotrope of oxygen and, when formed from oxygen via an endothermic reaction utilizing electrical discharge, heat, or ultraviolet light, it possesses a distinctive odor and strong oxidizing properties. These properties make ozone effective at killing bacteria and other pathogens, which is useful for wound treatment and sterilization.
In contrast, hydrogen peroxide (H2O2) is a widely used household disinfectant and skin antiseptic that breaks down into water and oxygen gas, which are environmentally safe. However, its use as a skin antiseptic can potentially cause damage to skin tissues, potentially delaying healing and leading to scarring. Despite this, hydrogen peroxide remains a prevalent choice for wound treatment and as an antiseptic in the United States due to its accessibility and efficacy in inducing healing when not overapplied.