One way marketers can trigger nostalgia in an individual is by:

A) increasing brand equity.
B) having the marketer's product present in their evoked set.
C) introducing a retro brand.
D) creating a new fashionable trend.

Introducing a retro brand can trigger nostalgia in individuals by reminding them of past experiences, products, or emotions associated with a previous era. This marketing strategy leverages the fond memories and sentiments people have for the past to create a connection with the product.