Which of the following commands should be used to determine if a remote print queue is down?（）

A. The external dump device is full. 
B. The dump device was not mirrored before the dump happened. 
C. The boot failed while copying the dump from paging space to a file. 
D. The dump device was not set to a paging device before the dump happened. 

A. Reboot the system.
B. Check the file system sizes.
C. Have the customer repeat the task to recreate the problem.
D. Inform the customer that no problems were found， and to call back if the problem reoccurs.