Viết lại câu bị động không ngôi theo cấu trúc 2 :
1. It is known that Ha Long Bay was recognised as a World Heritage Site by UNESCO in 1994
2. It is believesd that the best time to visit the complex of Hue Monuments is in April
3. It is reported that thousand of visitors come to enjoy breathtaking views of Ha Long Bay every year
4. It is claimed that Phong Nha - Ke Bang can be compared to a huge geological museum
5. It is understood that Binh Dai Fortress was designed to control movement on the Perfumed River
6. It is expected that the government will have measures to protect and preserve our man-made wonders