Which of the following tools is most effective for tasks requiring high torque?

The most effective tool for tasks requiring high torque is the impact driver. Impact drivers are specifically designed to deliver a strong rotational force and can produce high torque values better than the other options listed. They utilize a hammer-and-anvil mechanism to generate rapid bursts of torque, making them particularly suitable for driving screws and fastening bolts into tough materials.

This unique capability allows impact drivers to handle heavy-duty tasks and fasteners that would typically require significant effort with other tools. While ratchet wrenches can also provide leverage to generate torque, they do not produce the same level of impact force that an impact driver can deliver. Similarly, manual screwdrivers and adjustable spanners are not designed to provide the high torque needed for larger fasteners, making them less effective for high-torque applications.

In summary, the impact driver's design and functionality perfectly align with the demands of tasks that require high torque, making it the ideal choice in this context.