To solve this question, the user needs to have knowledge about the basic concepts of web forms and their inheritance in ASP.NET.

The correct answer is:

The Answer is: D

Explanation:

All web forms in ASP.NET inherit from the Page class. This class provides a set of methods, properties, and events that are used to build and interact with web pages. The Page class is defined in the System.Web.UI namespace, and it is the base class for all web forms in ASP.NET. The Page class provides a number of important features, such as the ability to handle user input, display dynamic content, and manage state information. Therefore, option D is the correct answer.

Option A is incorrect because the Window class is not related to web forms in ASP.NET.

Option B is also incorrect because there is no such thing as a Web class in ASP.NET.

Option C is incorrect because the Form class is not the base class for web forms in ASP.NET. It is used to create Windows Forms applications, not web forms.