How do you name the file containing the action controller class so the admin router matches the path to the class?

The module MyCompany_MyModule will add a new page to the admin interface at the URL path admin/mycompany/entity_grid.

A. Controller/Adminhtml/Entity/Grid/Index.php
B. Controller/Adminhtml/Mycompany/Entity/Grid.php
C. Controller/Adminhtml/Entity/Grid.php
D. Controller/Adminhtml/Mycompany/Entity_Grid.php