What is the difference between a screw and a bolt?

• A. A bolt is used with a nut, a screw is not
• B. A screw is used with a nut, a bolt is not
• C. Bolts are always longer than screws
• D. Screws have no threads

Answer: (A)

The main idea is how each fastener is used. A bolt is designed to pass through holes in parts and be secured with a nut on the other side, which clamps the pieces together. A screw is meant to be driven into a material or into a pre-tapped hole, creating holding power through its threads without needing a separate nut in most cases. So, the statement that bolts are used with a nut while screws are not reflects the typical usage pattern. There are exceptions (some screws can be used with nuts, and some bolts can go into tapped holes), but the general rule holds: bolt plus nut, screw into the material. The other options aren’t correct because screws do have threads, and length varies and isn’t the defining difference.