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: Physiology
Histamine is mainly found within storage granules of mast cells but also found in other tissues like: 
Select and explain. 
A. Gastric mucosa., B. Oral mucosa., C. Inner epithelium., D. All of the above.
A: Gastric mucosa.
Answer: A: Gastric mucosa. 
Explanation: Histamine is mainly found within storage granules of mast cell but also found in other tissue 

Mast cell histamine – mast cell and basophile. 
Non mast cell histamine – Gastric mucosa.