‘Heart block’ is a disease that can cause the heart rate to be lower than normal. A doctor discovered that electrical impulses were started normally, but they were not conducted correctly to the ventricles, so ventricular contraction rate was reduced. Which structure may be working incorrectly in the patient?
- A1 and 2 only
- B1 and 3 only
- C2 and 3 only
- D3 only