This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
In the human body, the action of surfactant is done by- 
Select and explain. 
A. Sugar & salt, B. Soap & water, C. Lipid and protein, D. Base and lipid
C: Lipid and protein
Answer: C: Lipid and protein 
Explanation: Ans. is 'c' i.e lipid and protein Approximate composition of a surfactantComponentPercentage compositionDipalmitoyl Phosphatidylcholine(DPPC)62Phosphatidylglycerol*5Other phospholipids10Neutral lipids13Proteins8Carbohydrate2DPPC and PG are types of phospholipids.Thus surfactant is made up of lipids and protein (and carbohydrate).Surfactant action by a molecule requires it to be amphipathic i.e. it should have both a polar group and a non polar chain; such a combination is possessed by lipids (phospholipids) & proteins.