Read the passage and do the tasks below. Floods are also one of the major and most dangerous types of natural disaster in Vietnam, constituting 37 percent of all disasters. The flood season in each region varies according the rainfall pattern. The flood season in the Red River and Thai Binh River system normally occurs from May to September, earlier than in other regions. The flood season on the rivers from Thanh Hoa to Ha Tinh is from June to October every year. On the rivers from Quang Binh to Binh Thuan, the flood season is from September to December. Flash floods and mudflow often occur in mountainous areas where steep slopes and high rainfall combine with inadequate drainage systems. Flash floods can also occur due to rupture of small reservoirs. Flash flood has occurred and is likely to occur across 33 mountainous provinces in the country in four regions: the northern mountains, central, central highlands and southeast. Flash floods are also more likely to occur as climate change continues. a. How is flood described as a natural disaster in Vietnam? __________________________________________________________________ b. When is the flood season? __________________________________________________________________ c. When is the flood season in the Red River system? __________________________________________________________________ d. When is the flood season in Quang Binh? __________________________________________________________________