What characteristic do synthetic ropes possess when they are clean and dry?

Synthetic ropes, when clean and dry, exhibit good dielectric properties. This means they are effective insulators and do not conduct electricity, making them particularly useful in applications where electrical hazards may be a concern. The dielectric properties are important in rigging operations, as they enhance safety when working near electrical sources.

The other characteristics mentioned do not accurately describe synthetic ropes in the context provided. For instance, synthetic ropes can have varying melting points, but they are generally lower than those of natural fibers, making high melting point an inaccurate choice. Additionally, synthetic ropes tend to have some elasticity, allowing them to absorb shock loads, which is contrary to low elasticity. Lastly, synthetic materials are designed to resist moisture absorption; therefore, they typically exhibit low moisture retention, rather than high. This resistance to moisture contributes to their durability and strength when used in various conditions.