Fill in the blank with a suitable pronoun:
She needs to choose a major between the two subjects. We don't know _______ one she would choose. [Intermediate]
Relative pronouns are used to refer to nouns mentioned previously. They could be people, places, things, animals, or ideas. They are also used to join two sentences.‘Who’, ‘whose’, ‘whom’ and ‘which’ are used as relative pronouns. ‘Which’ is apt here because it is used to denote an object or choosing something, especially between two choices, which is exactly the case here. Thus option B is correct. We use ‘who’ and ‘whom’ to speak about people, especially someone who has been referred to previously. ‘Who’ is used in the place of the subject of the sentence, like in “The students who work hard will pass”. While ‘whom’ is used in the place of the object of the sentence, like in “She is the girl whom I mentioned earlier”. Since the sentence doesn’t focus on the person, both ‘who’ and ‘whom’ are unsuitable. Thus options A and D are incorrect. On the other hand, we use ‘whose’ to denote to whom something/someone belongs to. Since the given sentence doesn’t focus on relationship or belonging, ‘whose’ cannot be used. For example, “This is Rita, whose brother has a band”. Therefore option C is incorrect.