When adding processors, which of the following elements should be identical? Choose all correct options.

A.
Brand and model

B.
Cache size

C.
Clock speed

D.
Bus speed and multiplier

E.
All of the above

Explanation:
You need to ensure processor compatibility when you add processors. The easiest way in which to ensure that added processors are compatible with existing processors is to ensure that the brand, model, cache size, clock speed, and bus speed and multiplier is the same.
References:

Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 380-381.