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: Pathology
Under polarised light, the congo red stained amyloid shows- 
Select and explain. 
A. Pink or red color, B. White color, C. Apple green birefringence, D. None
C: Apple green birefringence
Answer: C: Apple green birefringence 
Explanation: Answer- C. Apple green birefringenceAmyloid has an affinity for Congo red stain; therefore this method is used for confirmation of amyloid of all types. If the stained section is viewed in polarised light, the amyloid characteristically shows apple-green birefringence due to cross- b-pleated sheet configuration of amyloid fibrils.The stain can also be used to distinguish between AL and AA amyloid (primary and secondary amyloid respectively).