The correct option is A whatever
An adverb is a word which describes a verb, an adjective or another adverb in a sentence. The relative pronouns where, when, why, whatever etc act as adverbs when they join sentences or clauses. Therefore an adverb which introduces a relative clause is called a relative adverb. 'Whatever' is used for referring to anything or everything that happens or is available, needed, wanted etc. Thus, option B is the correct answer.