Why should CPU and network I/O be used to identify bottlenecks?

A.
Excessive consumption of CPU or network I/O indicates there are too many target devices.

B.
Excessive consumption of CPU or network I/O indicates a network misconfiguration.

C.
Excessive consumption of CPU or network I/O indicates that the anti-virus configuration could be causing a bottleneck.

D.
Excessive consumption of CPU or network I/O indicates that the system is low on virtual memory.