Complete the sentences with a definite article (the),an indefinite article (a/an) or zero article (-)

Rivers of the world
The Mekong River,(1).......tenth largest river in......(2)......world,has its origins in Tibet.(3)......first two thousand kilometers of (4)......river is in Chinese territory.It then flows 2,400 km through Myanmar,Laos,Thailand and Cambodia before entering (5)...... South China Sea through (6)..... huge delta in southern Vietnam sometimes called "the nine-tailed dragon".This area is known as (7)......Lower Mekong Basin.Hardly anywhere in (8) ...... world do more people depend on (9)
...... single river than in this region.Fifty million people live here and more than 80% of these are directly dependent on (10) ....... river through (11)...... fisheries and (12)......agriculture