Which of the following terms describe a short periods of time when the supply voltage is low?

A.
A spike

B.
Sags

C.
Brownouts

D.
A surge.

Explanation:
Sags are short periods of time when the supply voltage is low.
Incorrect
Answers:
A: A spike is a very high voltage level.
C: Brownouts occur over longer periods of time.
D: A surge is a voltage increase that occurs over a longer period of time References: Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 227-240.