CompTIA A+ Core 1 (220-1001) (#26)

During an inspection, it was found that data racks were not properly grounded. To pass the inspection and address a growing concern to protect data cabling and equipment, a technician must make sure all racks are properly grounded. Which of the following tools should the technician use to verify this has been completed?

Multimeter
Cable tester
Tone generator
Voltmeter