The usage of modal Verbs differ according to the the type of sentences.
Option B is correct because "Could" expresses authorization request.
Whereas, option A does not help in construct the sentence properly because have is always followed by past participle, which is absent in the given sentence; in option C the modal verb "would"in questioning sentences is generally used in asking someone about a preference. Therefore, "would" is not applicable in this sentence as the sentence is related to self interest; option D is incorrect as well because had is followed y past participle which is not present in the sentence.