This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Interleukin - 7 is produced by which one of the following - 
Select and explain. 
A. Macrophage, B. B cells, C. T cells, D. Stromal cells
D: Stromal cells
Answer: D: Stromal cells 
Explanation: Spleen,bone marrow stromal cells Reff: Anantganarayan & Panikers textbook of microbiology 9th edition pg:154 table 15.3