​The hygiene hypothesis holds that asthma is a result of _______ that has/have become common in modern society.

A) dust mites
B) ​cleanliness
C) ​cigarette smoking
D) ​industrial pollution

Hygiene Hypothesis

A theory suggesting that a lack of early childhood exposure to infectious agents, symbiotic microorganisms, and parasites increases susceptibility to allergic diseases by suppressing the natural development of the immune system.

Modern Society

Refers to the current state of social, economic, and technological development and organization in human societies.

Cleanliness

The practice of keeping oneself and one's surroundings clean, minimizing exposure to dirt, germs, and pollutants.