Final answer:
During the Restoration Period, spa resorts became popular amongst the upper class for leisure and medical purposes. They were a part of the culture of luxury and served as symbols of wealth and status, reflecting the broader societal trends of the time.
Step-by-step explanation:
The development of spa resorts during the Restoration Period can be understood best by first looking at the overall societal trends. The growing affluence of various strata of society, not just the traditional nobility, meant that there was new wealth to spend on leisure and recreation. This period saw the rise of middle-class values and the beginnings of mass leisure activities as commoners increasingly imitated the leisure pursuits of the nobility. Spa resorts became popular among the upper class as they served as a form of leisure, relaxation, and also as a place for medical treatments. It should be observed that spa resorts were not exclusively for the use of the lower classes and they were not unpopular during the Restoration Period.
One must remember that in the grander scheme of history, the aristocracy often engaged in leisure pursuits to demonstrate their wealth and status. The construction of luxurious homes, and the patronage of arts and culture, including the building of spa resorts, were commonplace among the upper echelons of society. Spa resorts became symbols of the luxurious lifestyles that the wealthy could afford. Therefore, the correct answer to the student's question regarding the development of spa resorts during the Restoration Period is that they became popular among the upper class for relaxation and for medical purposes.