Adjective clauses provide information about some noun in the sentence, which is the same function as adjectives. So an adjective would be "to tell the interesting story", where interesting gives some information about the story.
Similarly, "which is about wild ponies" is the whole adjective phrase - and this is the correct answer- gives some information about the story.
an off-record scource is just uncarted and/or hard to find. however, an anonymous scource has no specific author. someone would prefer to chose to speak to a reperter off the record probanly because they dont want to gain too much attention.
