A drilling bit which is doughnut shaped to permit recovery of the center portion of the hole drilled is called a __________.

Correct Answer: Option D — core bit

A core bit features a hollow, doughnut-shaped design specifically engineered to cut a cylindrical sample of the formation, known as a core, while leaving the center intact for geological analysis. This distinguishes it from standard bits designed to pulverize the entire rock face into cuttings for removal.