The Mekong River is one of the most important rivers in the world

4/ The Mekong River is one of the most important rivers in the world. It's the 7th (1)
river in Asia. It's about 4,350 kilometers long and (2)
China, Myanmar, Laos, Thailand, Cambodia and Vietnam. In Vietnam, the Mekong River is (3)
through six countries:
called by another name, the Cuu Long River, which has two (4)
: the Tien River
and the Hau River. People build houses and run their businesses on the rivers. The Mekong River is
home to more than 850 kinds of (5) fish. It is a very important (6)
1. A. long
B. length
C. longest
D. longer