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
Vagal stimulation of heart causes 
Select and explain. 
A. Increased heart rate, B. Increased R-R interval in ECG, C. Increased force of heart contraction, D. Increased cardiac output
B: Increased R-R interval in ECG
Answer: B: Increased R-R interval in ECG 
Explanation: None