Final answer:
Volkswagen's installation of musical stairs in a subway station as part of their marketing campaign is an example of guerilla marketing, aimed at engaging consumers in an unconventional, playful manner.
Step-by-step explanation:
In an example of guerilla marketing, Volkswagen set up a series of outdoor marketing experiences where they put the "Fun Theory" to the test. By installing musical keyboard bars as stairs in a subway station, they engaged users in a playful and unexpected way, which is a hallmark of guerilla marketing strategies. This tactic differs from sensory marketing, which focuses on stimulating the senses to influence behavior; stealth marketing, which attempts to market covertly; and viral marketing, which seeks to create content that spreads quickly online, often through social media platforms.
Answer: C) guerilla marketing.