Very aggressive pathogens such as the bacterium responsible for tuberculosis can easily overwhelm the protective features of the respiratory system. Less aggressive pathogens may be stopped by all of the following EXCEPT .

the olfactory epithelium

Explanation:

There are several protective features of the respiratory system which is responsible for stopping the less aggressive pathogens. Some of these protective features are:

Hairs in nose which trap pathogens like bacteria, virus from entering the lungs. The respiratory tract has mucus which is responsible for trapping the microbes and mucus have IgA antibodies which helps in eliminating these microbes. Alveolar macrophages engulf the pathogen and digest them

Olfactory is not a protective feature of the respiratory system and is responsible and adapted to detect the odor and transfer this signal to the brain.

The question is incomplete as it does not have the options which are:

The olfactory epithelium

Explanation:

The tuberculosis is a disease caused by the Mycobacterium tuberculosis. The tuberculosis disease affects the respiratory system from the nasal cavity to the respiratory passage.

The bacterium before infecting the human body has to fight with the natural immune system. The immune response produces the mucus which contains the antibacterial substances, the air filtration hairs in the nose which does not allow the entry of the bacterium and the macrophage which could ingest the pathogens.

The olfactory epithelium which is involved in the sensing the olfactory or smell from the surrounding environment is not involved in protecting the pathogen from the environment.

Thus, the olfactory epithelium is correct.