You have one Web application that contains several SharePoint site collections.
You need to create a Feature that adds a custom button to the Documents tab on the Ribbon of one site collection only.
What should you do?
A.
Create a new Feature. In a new <CommandUIDefinition> node, specify the location of Ribbon.Tabs._children.
B.
Create a new Feature. In a new <CommandUIDefinition> node, specify the location of Ribbon.Documents.Manage.Controls._children.
C.
Modify the CMDUI.xml file. In a new <CommandUIDefinition> node, specify the location of Ribbon.Tabs._children.
D.
Modify the CMDUI.xml file. In a new <CommandUIDefinition> node, specify the location of Ribbon.Documents.Manage.Controls._children.
Explanation:
MNEMONIC RULE: “create a new feature … Documents”You are interested in the group, so search for a group that matches close to the group name “Manage” and also should be present in a tab named “Document”. Here you go, the group name location “Ribbon.Documents.Manage”
Now, since you got your groupname… you have to specify that you are going to add a child control… the syntax is “Controls._children”. Hence your complete location is “Ribbon.Documents.Manage.Controls._children”
SharePoint 2010 Ribbon customization: Basics
http://howtosharepoint.blogspot.com/2010/06/ribbon-basics.html