A heavy, thick-walled tube, usually steel, used between the drill pipe and the bit in the drill stem to weight the bit in order to improve its performance is called a __________.

Correct Answer: Option B — drill collar

Drill collars are heavy-walled, high-strength steel tubes positioned immediately above the drill bit. Their primary function is to provide the necessary weight-on-bit (WOB) required for effective rock penetration and to maintain the drill string in tension, which prevents buckling and improves overall drilling performance.