Final answer:
Ionizing radiation is the most likely bactericidal option among those listed, as it can destroy the DNA and cellular components of microorganisms, causing their death. The correct option is B.
Step-by-step explanation:
Among the options provided - membrane filtration, ionizing radiation, deep-freezing, and lyophilization (freeze-drying), ionizing radiation is most likely to be bactericidal. Ionizing radiation, such as gamma irradiation, is capable of sterilizing heat-sensitive and packaged materials by breaking the DNA and other vital cellular components, leading to the death of microorganisms.
Membrane filtration is a method that physically removes microbes from liquid or air samples rather than killing them. Deep-freezing and lyophilization are preservation methods that do not necessarily kill microbes; they can merely inactivate them or preserve them in a state from which they can potentially be reanimated upon thawing or rehydration.
The effectiveness of chemical disinfectants has historically been compared to that of phenol, which was one of the first disinfectants used to kill or inhibit microbial growth. On the other hand, an antiseptic is suitable for use on living tissues to prevent infection, while a sterilant is an agent capable of eliminating all forms of microbial life, including spores.