My sister walked to school when she was a student.

48/50

My sister used to walked to school when she was a student.

My sister used to walking to school when she was a student.

My sister used to walks to school when she was a student.

My sister used to walk to school when she was a student.

Giải thích

Đáp án đúng: D

Cấu trúc used to + V để diễn tả thói quen trong quá khứ

Hướng dẫn dịch: Chị gái của tôi đã từng đi bộ đến trường khi chị ấy là một học sinh.