$\text{1.}$ D
$\text{→}$ Ho Chi Minh City is one of the biggest cities in the south of Vietnam <dòng 1>
$\text{2.}$ B
$\text{→}$ polution is the first thing that makes Ho Chi Minh City a worse place to live <dòng 11>
$\text{3.}$ A
$\text{→}$ Various means of transportation, especially millions of motorcycles, do contribute to the ever-increasing air pollution in Ho Chi Minh city <câu cuối>
$\text{4.}$ A
$\text{→}$ dwellers = residents: cư dân