You need to add a new field to a provisioned content type.

You must propagate the field to child lists and child content types.

What should you use?

A.
<AddContentTypeField>

B.
<ApplyElementManifests>

C.
<FieldRefs>

D.
<MapFile>

Explanation:
MNEMONIC RULE: “field for content type = AddContentTypeField”

AddContentTypeField Element (Feature)
http://msdn.microsoft.com/en-us/library/ff595314.aspx