WHY DOES THE AUTHOR MENTION A CHINESE TOY

5. - File thứ 1: De va dap an thi thu lan 2, Anh
Tiếng Anh File thứ 1: De va dap an thi thu lan 2, Anh
5. Why does the author mention a Chinese toy? A. To emphasize to complex design of helicopters. B. To contrast helicopters and fixed wing aircraft. C. To prove that helicopters were the first aircraft. D. To show that helicopter flight was envisioned in ancient times.