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
Serotonin, a mediator of inflammation in our body, is secreted /released by: 
Select and explain. 
A. Leukocytes, B. Endothelial cell, C. Mast cell, D. Platelet
D: Platelet
Answer: D: Platelet 
Explanation: Answer- D. PlateletSerotonin :It is found in the intestinal mucosa, brain tissue & platelets.Release of serotonin (and histamine) from platelets is stimulated when platelets aggregate after contact with collagen, thrombin, adenosine diphosphate (ADP), and antigen-antibody complexes.