I.

$\text{13.}$ Mrs. Quyen said she had to buy some oranges and some pomegranates.

$\text{→}$ HTD - QKD

$\text{→}$ have - had

$\text{→}$ I - she

$\text{14.}$ Liz said he was interested in the rice-cooking festival.

$\text{→}$ is - was

$\text{→}$ I - he

$\text{15.}$ Lan said she could sing English songs well.

$\text{→}$ can - could

$\text{→}$ I - she

$\text{16.}$ Peter said his sister would visit him the next week.

$\text{→}$ my - his

$\text{→}$ will - would

$\text{→}$ me - him

$\text{→}$ next week - the next week/ the following week.

13. Mrs. Quyen said that she had to buy some oranges and some pomegranates.

→ Lùi thì từ thì Hiện tại đơn về quá khứ đơn; I chuyển thành She vì chủ ngữ là Mrs.Quyen

14. Liz said that she was interested in the rice-cooking festival.

→ Lùi thì từ Hiện tại đơn về quá khứ đơn; I chuyển thành She vì chủ ngữ là Liz

15. Lan said that she could sing English songs well.

→ Lùi modal Verb là Can thành Could; I chuyển thành she vì chủ ngữ là Lan

16. Peter said that his sister would visit him the following week.

→ Lùi Will thành Would; chuyển me thành him vì tân ngữ là Peter; Next week chuyển thành The following week trong câu gián tiếp

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`\text{Chúc bn hk tốt!}`