Performance monitoring of a poorly performing system indicates a high level of CPU usage. Which tool can be used to help identify which processes are using excessive CPU resources？（）

Asystemadministratorreceivedthefollowingmessagewhiletry...

单项选择题A system administrator received the following message while trying to ssh to a server：  connection timed out.The administrator pinged the server and had no response. The administrator then pinged the gateway， and was successful. Which tool could the administrator use next to isolate the problem？（）

AusercallstoreporttheyaregettingI/Oerrorsonafilesystem....

单项选择题A user calls to report they are getting I/O errors on a file system. Which of the following tools should be used to isolate this problem？（）

Aremoteuseristryingtotelnettotheproductionserver.Theses...

单项选择题A remote user is trying to telnet to the production server. The session is getting a timeout error. Which command should the user issue to verify the network connection？（）