3 sentences

1. 这是越南的湄公河。

   zhè shì yuè​nán de méi​gōng​hé.

   This is the Mekong River in Vietnam.

   Source: CCMatrix

2. 湄公河自北向南流经该国。

   méi​gōng​hé zì běi xiàng​nán liú jīng gāi guó.

   The Mekong River flows through the country from North to South.

   Source: United Nations

3. 湄公河是世界上第十二大河流。

   méi​gōng​hé shì shì​jiè shang dì shí'èr dà hé​liú.

   The Mekong River is the 12th largest river in the world.

   Source: CCMatrix