Final answer:
An endoscope is used for common bile duct exploration. It is a medical device that allows doctors to look inside hollow organs and body cavities using a tiny camera attached to a flexible tube.
Step-by-step explanation:
The instrument used for common bile duct exploration is an endoscope. An endoscope is a medical device that allows doctors to look inside hollow organs and body cavities using a tiny camera attached to a flexible tube. It is inserted through various orifices or minor incisions in the body to visualize and explore internal structures.