Since the issue of the network connection dropping has been replicated on a known-good workstation using the same network cable, it suggests that the problem may not be with the individual workstations or the cable. The next logical step is to check for external interference, such as electrical or wireless interference that could be disrupting the network connection.

C. Validate the environment for external interference: External factors, such as nearby electronic devices or poor cabling, can cause intermittent network drops. Checking for interference would be a prudent next step.

Why the other options are incorrect:

A. Add new network hardware to reduce congestion: There’s no evidence that network congestion is the issue, and adding new hardware without identifying the cause is premature.

B. Assign a static IP to the impacted workstations: The issue appears to be related to the physical network connection or environment, not IP addressing.

D. Check the network logs for evidence of port flapping: Port flapping occurs when a network port rapidly switches between up and down states. While checking logs could provide information, external interference is a more likely culprit given the symptoms.

This issue is part of the Networking Troubleshooting domain in the CompTIA A+ Core 1 exam​.