The primary toxicity of pulmonary agents is to the and follows of smoke, particles, vapors, or gases

The primary toxicity of pulmonary agents is to the airway and follows inhalation of smoke, particles, vapors, or gases

Explanation:

Toxic substances which are in the form of gases, dust, vapors, fumes, fibers, etc. are able to penetrate organisms by inhalation through both the upper airways and the alveoli.

The respiratory system consists of the upper airways and the lungs.

The pathway of toxic substances through the respiratory system will depend on the body's reaction to these agents. Toxic substances are often grouped into particles and, depending on their size, do not even reach all the respiratory compartments.

it has one origin of replication, but it proceeds in two directions - d)