Final answer:
Autoclaving is the most widely used method of sterilization in the medical clinic, as it effectively destroys all forms of microbial life, including resilient endospores, by using moist-heat sterilization under high temperatures and pressures.
Step-by-step explanation:
The most widely used method of sterilization in the medical clinic is autoclaving (option a). Autoclaving utilizes moist-heat sterilization, where items are exposed to high temperatures and pressures above the boiling point of water to ensure the elimination of all forms of microbial life, including endospores which are known to be resistant to boiling temperatures.
Whilst ethylene oxide gas (option c) is a feasible sterilization method for heat-sensitive items and is commonly found in medical settings, it is carcinogenic and highly explosive and thus requires meticulous procedures and proper aeration after treatment. UV radiation (option d) is practical for surface sterilization but lacks the penetration power for thoroughly sterilizing medical equipment.
Consequently, autoclaving is deemed the superior choice for sterilization due to its efficacy in completely destroying all microbial life without the limitations faced by other methods such as ethylene oxide gas and UV radiation.