Card sorting is a user research method for designing or evaluating a site/product's information architecture. Participants group topics into intuitive categories and label these groups.
Key advantages of card sorting:
* Easy and fast to implement.
* Provides early user feedback and confirmation.
* Reveals natural user information grouping patterns.
Explanation of alternative methods:
* (A) Shadowing: Silent observation of user behavior.
* (B) Focus group: Group discussions for opinion gathering.
* (D) Survey: Questionnaires to collect data from multiple users.
Thus, option (C) is the correct choice.