Does this quiz question make sense?

I want to buy ____ books, two for my brother and the other for me.

A. all ; B. both ; C. three

I encountered this question in a quiz today. I choose answer C, but the answer key is A. I don't understand why. To me, the question itself doesn't make sense. First, I doubt the use of "the other". If the answer was A, then it should be the others for me. Also, "buy all books" doesn't sound quite right. "All the books" seems to make much more sense. Second, if I go for answer C, the structure "two ... the other" confuses me. Usually, I'd expect "one ... the other".

Any thoughts?

• Who wrote this quiz question? This is outrageous! – AIQ Dec 24 '19 at 11:08

A: I want to buy all books, two for my brother and the other for me.

B: I want to buy both books, two for my brother and the other for me.

C: I want to buy three books, two for my brother and the other for me.

You are correct that with A it should be "all the books", not just "all books". Although you could say "the others" (plural) afterwards, you'd probably be more likely to say "the rest":

A: I want to buy all the books, two for my brother and the others for me.

A: I want to buy all the books, two for my brother and the rest for me.

"the others" is more likely to be used for a small number, and "the rest" is more likely to be used for a large number. "all" implies a lot, which is why I say "the rest" would be more common. However, with the right context it could be as few as three:

Which book do you want to buy? The Cat in the Hat, The Little Prince, or The Very Hungry Caterpillar?

I'll buy all of these books.

With B it is grammatically correct but doesn't make sense since "both" is always two, so there would be no "other" for yourself.

With C it is both grammatically correct and makes sense. What is probably confusing you is the use of "other" as a pronoun. In this sentence it has the same meaning as "other one" or "other book".

C1: I want to buy three books, two for my brother and the other for me.

C2: I want to buy three books, two for my brother and the other one for me.

C3: I want to buy three books, two for my brother and the other book for me.

C1 and C2 sound the best. C3 is a little awkward because of the repetition of "book".

There is no grammatical difference between "one book for X and the other for Y" and "two books for X and the other for Y". It's just more common to have a division of two objects than three so you would have encountered it more often.

So the quiz is wrong. The best answer is C, not A.