You have a custom site definition.

You create a custom site Feature.

You need to ensure that the Feature is activated for all new sites that are created by using the custom site definition.

What should you do?

A.
Modify the Onet.xml file.

B.
Modify the web.config file.

C.
Add a Feature receiver to the custom site Feature.

D.
Add a Feature dependency to the custom site Feature.

Explanation:
MNEMONIC RULE: “custom site definition = Onet.xml”

You can perform the following kinds of tasks in a custom Onet.xml file that is used for either a custom site definition or a custom web template:

* Specify an alternative cascading style sheet (CSS) file, JavaScript file, or ASPX header file for a site definition.
* Modify navigation areas for the home page and list pages.
* Add a new list definition as an option in the UI.
* Define one configuration for the site definition or web template, specifying the lists, modules, files, and Web Parts that are included when the configuration is instantiated.
* Specify Features to be included automatically with websites that are created from the site definition or web template.

Understanding Onet.xml Files
http://msdn.microsoft.com/en-us/library/ms474369.aspx