When installing copper network cable in spaces that serve as air-handling plenums, safety regulations require the use of plenum-rated cable. Suspended ceilings used for ventilation fall into this category. CompTIA A+ emphasizes that plenum spaces require cable with low-smoke, fire-resistant insulation made from specialized materials that limit toxic emissions during combustion.

Plenum-rated cabling (CMP) is designed to meet strict fire codes such as NFPA 70 (National Electrical Code). It prevents smoke-filled ventilation pathways, which could rapidly spread fire or toxic fumes throughout a building. Standard PVC-jacketed twisted pair cables are not permitted in plenum spaces because they produce thick, toxic smoke when burned.

Multimode cable refers to fiber optics, not copper cabling. Coaxial cable is used for broadband and certain RF applications but does not inherently meet plenum safety requirements unless specifically plenum-rated. Twisted pair describes the cable’s internal structure (Cat5e, Cat6, etc.), but it does not indicate the type of jacket. Only plenum-rated twisted pair is acceptable.

Therefore, the correct answer is Plenum, as it ensures compliance with safety standards and building codes, prevents hazardous conditions, and aligns with CompTIA best practices for structured cabling installations.