A device used to enlarge the size of an existing bore hole, having teeth arranged on its outside circumference to cut the formation as it rotates is a(n) __________.

Correct Answer: Option C — hole opener

A hole opener is a specialized drilling tool designed to enlarge an existing borehole. It features cutters or teeth on its outer circumference. As the tool rotates, it removes formation material, increasing the diameter of the hole to accommodate larger casing strings or specific drilling requirements.