What term describes a text file that maintains state and tracks user activities in web applications?

The term that describes a text file that maintains state and tracks user activities in web applications is "cookie." Cookies are small pieces of data stored on the client's computer by the web browser while browsing a website.

When a user interacts with a web application, the server can create and send cookies to the client as a way to remember information about the user between sessions or during browsing. This could include preferences, login status, or any other state information necessary for a web application to provide a personalized experience. Cookies can store simple text data and are sent back and forth between the client and the server with each request, allowing the server to recognize returning users and maintain continuity in user sessions.

The other options do not fulfill the same role as cookies: a drop zone typically refers to an area in a user interface for file uploads, a client refers to the device or application that accesses a service, and the application cache is used for storing resources for offline use, rather than specifically tracking user data.