Doing which of the following during peak production hours could result in unexpected downtime?

A.
Performing data migration or tape backup

B.
Performing preventive maintenance on electrical systems

C.
Promoting applications from development to the staging environment

D.
Replacing a failed power supply in the core router of the data center

Explanation:
Choices A and C are processing events which may impact performance, but would not cause
downtime. Enterprise-class routers have redundant hot-swappable power supplies, so replacing a
failed power supply should not be an issue. Preventive maintenanceactivities should be scheduled
for non-peak times of the day, and preferably during a maintenance window time period. A mishap
or incident caused by a maintenance worker could result in unplanned downtime.