The correct answer is: A. Solution Explorer Window
The Solution Explorer window is a visual representation of the projects and items that make up your solution. It displays the list of projects contained in the current solution, as well as the files and folders within each project. You can use the Solution Explorer window to open, close, and manage projects and files, and to view the properties of items in your solution.
The List Window displays a list of all the items in the current solution. It can be used to quickly find a specific item, and to open and edit it.
The Project Window displays the contents of a single project. It can be used to view and edit the files in a project, and to add and remove files from the project.
The Catalogue Window displays a list of all the components that are available for use in your solution. It can be used to find and add components to your solution.