Which of the following can be described as a blackout?

A.
Impulses are short-term power conditions.

B.
Short-term, low-voltage conditions, produced by power utilities unable to meet demand.

C.
A complete loss of utility power.

D.
None of the above.

Explanation:
A blackout is a complete loss of utility power, which can be caused by grid over-demand, lightning strikes, downed or iced power lines, natural disasters, or accidents.
Incorrect Answers:
A: Spikes and surges, also called impulses, are short-term power conditions that push voltage above 110 percent of nominal.
B: Power sags are short-term, low-voltage conditions, produced by power utilities unable to meet demand.
References:

Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 227-240.