Final answer:
The bar soap that was marketed with just one scent, Ulster Fragrance, until the 1990s is Ivory. This reflects historical marketing strategies and consumer product knowledge from that era.
Step-by-step explanation:
The question revolves around a historical marketing fact about a certain brand of soap—which until the 1990s was marketed with just one scent, known as Ulster Fragrance. Of the options given, namely Dove, Ivory, Zest, and Dial, the correct answer reflects the soap history and marketing strategies of the time.
Industrially manufactured bar soaps have been available since the late 18th century, with their use becoming widespread in industrialized nations owing to a heightened awareness of the importance of hygiene. This is due to the fact that good hygiene practices are key in reducing the population size of pathogenic microorganisms, a notion that has been heavily promoted through various advertising campaigns throughout history.
Amongst the options provided, Ivory is the brand that was marketed with Ulster Fragrance until the 1990s. Ivory is known for its simple and gentle formula and has recognized the importance of associating a unique scent with its brand to resonate with consumers. Finding the correct match to the historical fact requires knowledge of branding and consumer products from this era.