Which of the following causes discolored ceiling?

A.
Presence of dust

B.
Water leak

C.
ESD

D.
None of the above

Explanation:
Discolored ceiling tiles can indicate the existence of some type of water leak.
Incorrect
Answers:
A: Dust on the equipment can cause overheating.
C: The server room should also be reasonably humidified to reduce the likelihood of damaging electrostatic discharge (ESD) occurring.
References:
Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 473