A Linux administrator is troubleshooting SSH connection issues from one of the workstations.
When users attempt to log in from the workstation to a server with the IP address 104.21.75.76, they receive the following message:

The administrator reviews the information below:


Which of the following is causing the connectivity issue?

A. The workstation has the wrong IP settings.
B. The sshd service is disabled.
C. The server's firewall is preventing connections from being made.
D. The server has an incorrect default gateway configuration.