Chlamydia is a primary pathogen
Cardio-Pulmonary Resuscitation also known as CPR. This chain of survival is the first-aid command for patients or individuals who are experiencing life-threatening situations at a given time. Highly-skilled and trained individuals are the only ones allowed to perform this as it may result to different kinds of complications if administered incorrectly.
The correct answer is this one: "human industrialization." Air pollution comes from human industrialization. Because of too much industrialization, there are a lot of excess and wastes in any form: air or even liquid and solid wastes.