What is a key difference between bolts and screws?

The distinction you're focusing on relates to the use of nuts with fasteners. Bolts are typically designed to be used in conjunction with nuts, allowing for a secure connection that can withstand various stresses and loads. The ability to pair a bolt with a nut enables the two components to create a strong and effective fastening solution, especially in applications requiring high strength and durability.

In contrast, screws are generally designed to be driven directly into material without the need for a nut. They create their own threads within the material, providing a secure hold. Hence, while both bolts and screws serve the purpose of fastening, their designs and applications differ, particularly in their interface with nuts. This unique feature of bolts is what makes this answer correct, emphasizing the functionality and application of the two types of fasteners.