This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Physiology
True statement regarding the alveolar epithelial cells: 
Select and explain. 
A. Gas exchange occurs the type II pneumocytes, B. Lamellar inclusion bodies are seen in type I pneumocytes, C. Type III pneumocytes act as chemoreceptors, D. Type II and type I exist in a ratio of 2:1
C: Type III pneumocytes act as chemoreceptors
Answer: C: Type III pneumocytes act as chemoreceptors 
Explanation: Gas exchange occurs across type I pneumocytes. Option A is incorrect. Type II pneumocytes synthesize surfactant. When there is alveolar injury, type I cells degenerate and are replaced by type II cells. Type II cells are thus responsible for regeneration of epithelium. Lamellar inclusion bodies are the structures within which surfactant is present, in type II pneumocytes. These bodies then release surfactant by exocytosis. Type III pneumocytes act as chemoreceptors. Type I and type II pneumocytes exist in a ratio of 1:1. Option D is incorrect.