Final answer:
The fourth principle in the HACCP system is to verify that the system works.
Step-by-step explanation:
The fourth principle in the HACCP (Hazard Analysis and Critical Control Point) system is to verify that the system works. This involves conducting regular audits and inspections to ensure that the procedures and controls put in place are effective in preventing food safety problems. Verification activities may include reviewing records, conducting microbiological testing, and evaluating the overall performance of the system.