Sprinkler risers subject to mechanical damage shall be protected by:

Sprinkler risers that are susceptible to mechanical damage require appropriate protection to ensure their functionality and reliability during a fire event. The correct approach involves the use of protective guards specifically designed to shield the risers from potential impacts or damage that could be caused by equipment, vehicles, or other objects in the vicinity.

Protective guards serve as a physical barrier, effectively minimizing the risk of damage to the sprinkler riser, which is critical for maintaining the integrity of the fire protection system. While wrapping with tape or providing no protection might seem like potential options, these methods do not offer a reliable or effective level of protection needed to safeguard sprinkler risers from mechanical impacts.

In summary, using protective guards is the most effective solution for preventing mechanical damage to sprinkler risers, ensuring that they remain fully functional and capable of delivering the required water flow in the event of a fire. This is why the correct answer includes the necessity for protective guards along with the implied understanding that the other options do not provide suitable protection.