Which of the following is NOT a type of sprinkler system?

The correct answer identifies a type of sprinkler system that does not exist in standard terminology in the fire protection field. Wet and dry sprinkler systems are well-established types of systems used for fire suppression. A wet sprinkler system contains water at all times and is activated when a fire is detected, providing immediate response. A dry sprinkler system, on the other hand, is filled with pressurized air or nitrogen and releases water only when the system is activated, making it suitable for environments where freezing could occur.

The term "compressed" is not a recognized type of sprinkler system, distinguishing it from the others. While "combined" may suggest a system that integrates various features or technologies, it is not a standard classification like the wet and dry systems. Understanding the correct classifications of these systems helps ensure proper installation and maintenance in fire safety applications.