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: Anatomy
JG cells (Juxta glomerular apparatus) are ? 
Select and explain. 
A. Macula densa, B. Smooth muscular cells of afferent aeriole, C. Smooth muscular cells of afferent aeriole, D. Islets of epithelial cells
B: Smooth muscular cells of afferent aeriole
Answer: B: Smooth muscular cells of afferent aeriole 
Explanation: B i.e., Smooth muscle cells of afferent aeriole