Click the Exhibit button. 
From a local machine， connectivity with a server named server1.comptia.org is checked. It cannot be reached， but it can  be accessed via the IP address.  
Which of the following is the MOST common cause of this error？（）

 
 

A. The server is down.
B. The DNS server is down.
C. The local DNS cache is full.
D. The local DNS client is stopped.
E. The local DNS cache is corrupted.