The MekongRiver,(25) ________________ Southeast Asia, is the world's 12th—longest river andthe 7th longest in Asia. It's about 4.350 kilometres (26) _______________ and flows through six countries, including China, Myanmar, Laos, Thailand, Cambodia and Vietnam. When flowing into Vietnam, the Mekong River is also called Cuu Long River, (27) __________________ has two branches: Tien River and Hau River. People build houses and run their businesses on the rivers. The Mekong River is (28) _______________ to more than 850 kinds of fresh water fish. 25. A. in B. on C. by D. at 26. A. longest B. length C. lengthen D. long 27. A. that B. whom C. which D. where 28. A. place B. home C. region D. country