Pulmonary surfactant is:

 # Pulmonary surfactant is:

A. Lecithin

B. Dipalmitoyl phosphatidyl choline

C. Dipalmitoyl phosphatidyl serine

D. Sphingosine

The correct answer is B. Dipalmitoyl phosphatidyl choline. 

Pulmonary surfactant is a complex mixture of lipids and proteins that is produced in the lungs and helps to reduce surface tension in the alveoli during breathing. Dipalmitoyl phosphatidyl choline (DPPC) is the most abundant lipid in pulmonary surfactant and is the primary component responsible for its surface tension-lowering properties.

Reference: Hall, J. E. (2016). Guyton and Hall textbook of medical physiology (13th ed.). Philadelphia, PA: Elsevier. Chapter 44, Pulmonary Ventilation.