A. Create partial classes for the controllers that have AJAX functionality to create a set of Controller.Ajax.cs files. Put the AJAX-specific functionality in those files
B. Create an area called AJAX. Move the specific AJAX functionality into the Controllers directory and leave the Views and Models directories empty
C. Create a new ASP.NET MVC 4 application project. Move the AJAX functionality into that so that it will be more responsive
D. Create an area called AJAX. Move all controllers, models, and views into the area