Answer:
Phagocytic defense in the normal lung is shared principally by two kinds of cells - alveolar macrophages that reside on the air surface and roam the alveoli and PMNs that circulate in the intravascular space or are stored transiently in areas adjacent to the capillary-alveolar interface (marginated in capillaries)
Explanation:
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I believe it is the nucleus.
The correct answer is D. species.
The definition of a species is termed as a group of interbreeding individuals cannot be easily applied to organisms that they reproduce only or mainly by asexual methods.
Species is termed as the basic unit of classification and taxonomic rank and also unit of biodiversity. It is the largest group of organisms whereby two individuals produce fertile offspring.
They are typically by sexual reproduction. Boundary which is between closely related species they becomes unclear.