Which of the following can transfer power between two turning shafts located at right angles?

Worm gears are specifically designed to transfer power between two shafts that are oriented at right angles to each other. This unique configuration allows for a compact design while providing a high gear reduction ratio, making them particularly useful in applications where space is limited or where significant torque conversion is necessary. The worm gear consists of a screw (the worm) that meshes with a gear (the worm wheel), enabling the transfer of motion and power efficiently between the non-parallel shafts. This ability to change the direction of power transmission while handling heavy loads is what distinguishes worm gears from the other types of gears listed.

Spur gears, for instance, are typically used for parallel shaft arrangements and do not facilitate the transfer of power through right-angle configurations. Rack and pinion gears convert rotary motion into linear motion, but they also do not change the direction of rotation through right angles. Herringbone gears, while capable of handling axial loads, are used for parallel shafts and do not alter the angle of shaft connection either. Therefore, the ability of worm gears to handle the specific task of power transfer at right angles makes them the correct answer in this context.