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
Platelet derived growth factor is released in vessels from: 
Select and explain. 
A. Endothelial cells, B. Fibroblasts, C. Macrophages, D. Alpha granules
D: Alpha granules
Answer: D: Alpha granules 
Explanation: Platelet activation:
  The adherent platelets get activated, undergo a shape change and degranulate. The granules in the platelets can be

Alpha  granules  having  P-selectin,  fibrinogen,  fibronectin,  factors  V  and  VIII, platelet  factor  4,  platelet-derived  growth  factor,  and  transforming  growth factor-β.
Delta  granules  or  delta  bodies  having  ADP,  ATP,  ionized  calcium,  histamine, serotonin, and epinephrine.