Final answer:
The telephone wiring in a plenum space is likely to use plenum-rated cable, which is designed to be flame-blocking and emit less toxic fumes than standard cables, ensuring compliance with building codes and safety.
Step-by-step explanation:
The question regarding telephone wiring in a plenum space concerns the type of cable that is likely to be used due to the air circulation for heating and air conditioning systems within buildings. The correct choice for this application is plenum-rated cable, which is designed to blocking the spread of flames and not emit toxic fumes when exposed to heat or fire. It is more expensive than standard cables but essential for meeting building codes and ensuring safety in plenum spaces.