What component transfers torque from a shaft to a chain?

The correct choice is a sprocket because it is specifically designed to transfer rotational motion and torque from a shaft to a chain. Sprockets have teeth that engage with the links of a chain, allowing effective power transfer while minimizing slippage. This engagement is essential in applications such as bicycles, motorcycles, and various machinery where a reliable and efficient connection between the shaft and the chain is required.

While components like couplings, sheaves, and pulleys are important in different contexts, they do not perform the same function in relation to a chain. Couplings are used to connect two shafts and transmit torque between them without misalignment. Sheaves and pulleys are intended for belt-driven systems, where a belt rather than a chain is the means of power transfer. Thus, for the specific function of interfacing with a chain and ensuring the transfer of torque effectively, a sprocket is the appropriate component.