The correct option is B Either ; or
A conjunction combines or connects two sentences as one. They can be a word or a phrase (like even if, as well as, etc). Correlative conjunctions are words in pairs that connect two sentences, but they're not written together, for example, either...or, but...and, such...that etc, where a word or a phrase is in between the pair (either rice or noodles). In the given sentence, there's a choice between two people, "Marge, Clive" out of which one person would show the listener "you" the room. A pair of conjunctions is required that refers to choice. 'Either...or' is used in the affirmative sense to refer to a choice between two possibilities, or people, like the given sentence. Hence option B is correct. 'Neither...nor' is the negative equivalent to 'either...or', it can't be used in this sentence, because it's in the affirmative. This is determined by the sentence that follows "Kendra is busy", so that means one of the two, Marge or Clive, would show the person to their room. If the second sentence went like this 'They're both busy', then option C would have been correct as well, otherwise it's incorrect. 'Either' is always paired with 'or', as they're in the affirmative, and 'neither' with 'nor', as they're in the negative. Either can't be paired with nor and neither with or. Also, 'nor' is generally not used where 'neither' is also not used. Hence, options A and D are incorrect.