A patient visits your clinic often with recurrent respiratory infections. Based upon their medical history, it appears they have been an active smoker for over 40 years. Select the statement that most accurately reflects how this information may reveal why the patient is highly susceptible to respiratory pathogens:

1. smoking decreases the formation and effectiveness of complement proteins.
2. smoking can paralyze the ciliary escalator.
3. smoking directly inhibits B- and T-cell action.
4. smoking decreases the activity of neutrophils.

Respiratory infections affects the sinuses, lungs, chest and nose. Chronic infections occurs repeatedly over time. Bacteria and virus may also acts as pathogen for the respiratory infections.

The main reason of the respiratory infection is the presence of harmful chemical in smoking. The motile cilia connects the ciliary escalator with the trachea and respiratory system. The harmful toxins and chemicals in smoke can paralyze the ciliary escalator.

Thus, the correct answer is option (2).