Answer:
Option C is correct.
Explanation:
Observation is a market research technique, used to analyze the behavior of consumers into a specific market area.
In your example, Bianca wants to know which other stores her customers visit, in other words, she wants to study her market and the behavior of her, customers; what is behind their choices?, what motivates them? This will help her to launch successful marketing campaigns, and to stand out from the competition.