Sentence Correction

With diamonds, as with all gems, one should ask for a written description of one's
purchase; the description may prove useful later if you have reason to believe the
jeweler misled you.
(A) one should ask for a written description of one's purchase
(B) you should ask for a written description of your purchase
(C) a written discretion of your purchase is what one should ask for
(D) a written description of one's purchase is what should be asked for
(E) a written description of your purchase is what should be asked for

The correct answer is B.
You need to be consistent with regard to pronouns used in the whole sentence. Since "you" appears in the non-underlined part of the sentence, it is necessary to use it also in the underlined part. Therefore, all answers which include "one" are incorrect.
In answer E "one" is not used but this answer is much less concise than B.