Correct option is D
When the distance between two pulleys becomes very large (more than 8 metres), rope drives (circular belts) are preferred over flat or V-belts. This is because rope drives are specifically designed for long-distance power transmission and can handle higher loads with better efficiency over such distances.
A circular belt (rope drive) consists of ropes (usually made of fiber or steel wire) that run over grooved pulleys. These ropes provide:
Better grip due to groove contact
Reduced slip over long spans
Capability to transmit large power over long distances
