It depends on what is asked of you/underlined. If "storks symbolize good luck and welcome stork nests on their chimneys" is underlined, then the correct answer is A. It is an independent clause, completed and can exist on its own, it doesn't need to be supplemented. It is not a noun clause, or an adverb clause (because there is no adverb), or adjectival clause, since there is no adjective.
