An entire enterprise cannot access a specific website. The network technician knows the website was accessible last week. The technician can also ping the website. Which of the following is the technician MOST likely to find upon investigation? 

Answer options:

A. The firewall is misconfigured.
B. The network is being hit by a zero-day attack.
C. The SSL certificate is untrusted.
D. The SSL certificate has expired.

D