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
Most important for diapedesis 
Select and explain. 
A. PECAM, B. Selectin, C. Integrin, D. Mucin like Glycoprotein
A: PECAM
Answer: A: PECAM 
Explanation: Diapedesis or Transmigration-process of leukocyte recruitment is migration of the leukocytes through the endothelium.

Most important for diapedesis is PECAM- 1 and CD31 molecules