CompTIA Network+ Question A-5

A customer is attempting to download a file from a remote FTP server, but receives an error that a connection cannot be opened. Which of the following should be one FIRST to resolve the problem?

A. Ensure that port 20 is open
B. Ensure that port 161 is open
C. Flush the DNS cache on the local workstation
D. Validate the security certificate from the host

Correct Answer: A