Final answer:
Among the provided options, the air-conditioning unit is the best example of a closed loop system because it uses feedback in the form of a thermostat to regulate and maintain a desired temperature. the correct option is (b).
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Step-by-step explanation:
The question at hand is asking which of the provided options is an example of a closed loop system. A closed loop system is one where the operation is regulated by feedback that allows the system to adjust its performance to meet a desired output.
Out of the options provided:
An air-conditioning unit is a classic example of a closed loop system. It uses a thermostat to measure the temperature and adjust cooling or heating to maintain a set temperature.
In the context of the additional provided information, a mass on a spring in a vacuum is also a closed system because once it is set into motion, it does not interact with its environment—no energy or mass enters or leaves the system, idealizing a perfectly conservative system. This is in contrast to an open system, where energy or mass can be transferred into or out of the system, such as when a bullet becomes embedded in a wooden block.
Therefore, the best example of a closed loop system among the options is B. Air-conditioning unit.