A contractor was hired to troubleshoot congestion issues on the network. After a few of the switches have been reconfigured/upgraded by the contractor, congestion worsens and collisions increase. Which of the following is the BEST action to alleviate the situation?
A. Allow the contractor to reset switches to factory defaults
B. Check the cabling on all switches for improper crossover use
C. Document the changes that were made
D. Downgrade firmware and restore backup configuration