In the following essay, each blank has fou

问题：

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.
The key to SNMP (76) is its simplicity. It has a small command set that does a good job of collecting information from (77) any network device. In a SNMP environment, (78) of the work is handled by the network management system. Devices that are being managed are not (79) with processing (80) that might affect their performance.

A．time

B．power

C．speed

D．overhead