You Want to Add Additional XML ("Additional XML Declaration") to an Existing

You want to add additional XML ("Additional XML Declaration") to an existing layout block. Which is the proper tag for adding it?

A) <reference type="block">Additional XML Declaration</ reference>
B) <action method= "addNewBlock"><block name>Additional XML Declaration <I block name></ action>
C) <reference name="block.name">Additional XML Declaration</reference>
D) <method action= "setBlockContent"><xml>Additional XML Declaration</xml></method>