This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neoplasm of Mature B & T Cells, Subject name: Pathology
Post transplant lymphoma occurs due to proliferation of which of the following cells? 
Select and explain. 
A. T cell, B. B cell, C. NK cell, D. Monocyte
B: B cell
Answer: B: B cell 
Explanation: Post transplant lymphoma (Post transplant Lymphoproliferative Disorder or PTLD) occurs due to proliferation of B cells