___________________ are units of measure based on performance counters that are native to the local
operating system and are configurable
indicators that can alert an administrator to a problem over media such as e-mail, SMS, or SNMP.

A.
Counters

B.
Items

C.
Instances

D.
Metrics

Explanation:
Metrics are units of measure based on performance counters that are native to the local operating system.
Metrics are configurable indicators
that can alert an administrator to a problem over media such as e-mail, SMS, or SNMP.