What is the reason users cannot access a secure website hosted on a server if port 443 is closed?

When accessing a secure website, the communication between the user's browser and the web server typically occurs using HTTPS, which operates over port 443. If this port is closed, the server will not be able to receive or respond to secure requests from clients trying to establish a connection. Consequently, users would be unable to access the secure website since their requests would not reach the server, and the server would not send any response back.

The other options, while potentially relevant to other types of connections or services, do not directly impact the ability to access a secure website. Port 22 is associated with SSH (Secure Shell), port 80 is used for standard HTTP traffic (non-secure), and port 3389 is used for Remote Desktop Protocol (RDP). None of these ports affect the HTTPS protocol, which solely relies on port 443 for secure connections. Thus, the closure of port 443 is the critical factor preventing access to a secure website.