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Câu hỏi: 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.
Genetic engineering (A) is helping researchers unravel the mysteries of (B) previously incurable diseases (C) so that they get to (D) its root causes and find cures.
A. is helping
B. previously
C. so that
D. its
Genetic engineering (A) is helping researchers unravel the mysteries of (B) previously incurable diseases (C) so that they get to (D) its root causes and find cures.
A. is helping
B. previously
C. so that
D. its
- diseases dạng số nhiều nên phải thay "its" bằng "their"
Đáp án D.