This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Gap junctions are found in 
Select and explain. 
A. Intestine, B. Brain, C. Kidney, D. Cardiac muscles
D: Cardiac muscles
Answer: D: Cardiac muscles 
Explanation: Gap junction forms tunnels that join the cytoplasm of two cells. They permit the substance to pass from one cell to adjacent cells. It also helps in propagation of action potential from one cell to another. (REF: GANONG'S REVIEW OF MEDICAL PHYSIOLOGY)