What type of cable must be used when running cables between floors of a structure?

The correct choice is riser cable. Riser cables are specifically designed for vertical spaces between floors in a building. They have fire-resistant jackets that help to prevent the spread of flames and smoke through the building's riser shafts. This is critical for safety in multi-story structures, as these vertical pathways can allow fire to travel quickly from one floor to another if not properly equipped with appropriate cabling.

Riser cables are typically used for data and voice transmission and are compliant with building codes for riser applications. They are structured to limit the risk of fire hazards, making them essential for installations where cables run up through multiple floors.

Plenum cables are designed for spaces where air circulation is necessary, typically in ceilings or under floors that handle air movement for heating and cooling systems, and while they are also fire retardant, they are not specifically suited for vertical riser applications.

Coaxial cables are used primarily for transmitting television and internet signals but do not serve the same safety considerations for running between floors.

Twisted pair cables are typically used for networking and telecommunications but do not provide the specific fire-resistance features required for riser setups, nor are they specifically designed to mitigate fire spread in vertical shafts.