What is the primary function of screwdrivers?

The primary function of screwdrivers is to turn screws. They are specifically designed to engage with the head of a screw, allowing the user to drive the screw into materials or remove it from them. The shape of the screwdriver's tip, whether it be flat, Phillips, or another style, corresponds to the design of the screw head, ensuring a secure fit that minimizes the risk of slipping or stripping the screw.

In the context of the other choices, while tools may grip round objects, measure torque, or connect wrenches, these functions are not related to the core purpose of a screwdriver. Instead, screwdrivers are uniquely tailored for fastening and unfastening screws, making this function the reason they are essential in various tasks, from assembly to repairs.