Answer:
D. They are foolproof
Explanation:
The intrusion detection systems can tell you if there is an intruder but the action after the detection to stop the intruder is made by humans. Â Depending on the technology used in the system, the false alarm can be created by different situations. For example, an infrared detector can be affected by the weather and send a false alarm. The detectors need to be plugged into a constant power supply to work. But the systems of intrusion detection aren't foolproof.