Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

Their pioneering research showed that the learning motivation of the two groups of learners was quite distinctive from each other, and the comparative group whose learning motivation was stronger performed better than the control group.
Ghi chú: Câu này có sửa lại đáp án để có thể chọn được khi làm bài trên hệ thống