Question

Which word correctly completes this conversation?

Answer 1

Answer: The right answer is the C) aquélla.  

Explanation: Just to elaborate a little on the answer, it can be added that these words are demonstrative adjectives (this, that), and they indicate how far away is, in time and in space, the said thing or person the speaker is talking about. Since the word guitarra is feminine, you can discard options A and D, which must be used with masculine words. Likewise, since the guitar is in a corner of the room, it is not close by, so you cannot use "ésta" (with an accent). The right answer is, therefore, "aquélla," which translates as "that one."    

Answer 2

The correct answer is aquella, because we would use the word if there was a difference in the distance. Like if you were in the right corner of a room, and the guitar was at the left corner of the room. And another reason is because aquella is feminine and in spanish, guitar is feminine.