I would believe that the Answer is C
Answer:
Respiratory epithelial cells line the respiratory tract from trachea to bronchi into bronchioles and alveolar sacs. ... The goblet cells produce and secrete mucous to trap pathogens and debris within the airway tract. Basal cells are progenitor cells that differentiate into cells types found within the epithelium.
The answer is: They exists only in the Northern Hemisphere.
It is possible to find a glacier in other spots in the world.
I would say man made but not to sure with out answer choices..
