During the inspection of operation equipment, which of the following statements is correct?
A . You can check the memory usage of the device by executing the display memory-usage command. If "Memory Using Percentage Is" exceeds 80%, you need to pay special attention currently.
B . You can check the running status of the board by executing the display device command, the “Online” of the board should be “Present”
C . You can view the fan status by executing the display fan command. When the Present item is NO, it means normal
D . You can view the FTP network service port by executing the display ftp-server command, and the unused FTP network service port needs to be recorded
Answer: B