Which individual is credited with inventing the roller-cone drilling bit?

• A. Thomas Edison
• B. Nikola Tesla
• C. Howard Hughes
• D. Henry Ford

Answer: (C)

The key idea is identifying who brought the roller-cone style drill bit into practical use for oil drilling. A roller-cone bit uses three rotating cones with teeth that grind rock as the drill advances, giving better cutting action, wear resistance, and durability in hard formations compared to earlier designs.

Howard Hughes (Sr.) is credited with inventing and commercializing this roller-cone (tri-cone) bit, founding Hughes Tool Company and transforming drilling technology in the early days of modern rotary drilling. This invention significantly boosted penetration rates and reliability in challenging geology, which is why it’s associated with his name.

The other figures are famous for breakthroughs in unrelated fields—electric power and devices, or mass production in automobiles—so they don’t fit as the inventor of this drilling tool.