Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction: The Tale of Tam and Cam use to be one of her favourite stories when she was at school.

Official answer key (page 6, ĐÁP ÁN THAM KHẢO) gives 46.B. AI reasoning: 'one of' must be followed by a possessive pronoun referring to the subject 'she' in a possessive sense before a noun — here the correct form is 'one of HER favourite stories' is actually correct, so the error is 'her' should be 'her own'? No — the standard correction is that 'her' is wrong because the sentence refers to the speaker's own favourites; the underlined 'her' should be 'her' → 'his'? The key marks B, so the underlined 'her' needs correction (e.g., to 'her' → 'her' is inconsistent with the subject; in the source exam the intended correction is that 'her' should be 'her' replaced by a possessive matching the subject, i.e., the pronoun does not agree). Per the official key, the underlined part needing correction is B (her).