Detailed Solution:
The correct answer is “1 only”.
The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia.
From the Tibetan Plateau the river runs through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam.
The Mekong Delta in southern Vietnam is a vast maze of rivers, swamps and islands, home to floating markets, Khmer pagodas and villages surrounded by rice paddies.