A sag occurs when the ___________.

A.
supply of voltage is low for a long period of time

B.
voltage increases occurs over a longer period of time

C.
supply of voltage is low for a short periods of time

D.
None of the above.

Explanation:
When the power supply drops below normal levels, sags and brownouts occur. Sags are short periods of time when the supply voltage is low.
Incorrect Answers:
A: Brownouts occur over longer periods of time
B: 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.