Which of the following can be defined as the set of allowable values that an attribute can take?

A.
domain of a relation

B.
domain name service of a relation

C.
domain analysis of a relation

D.
domains, in database of a relation

Explanation:
The domain of a relation is the set of allowable values that an attribute can take. In other words, it is the values
that can be entered in a column (attribute) of a table (relation).

Stewart, James, Ed Tittel and Mike Chapple, CISSP: Certified Information Systems security Professional Study
Guide, 5th Edition, Wiley Publishing, Indianapolis, 2011, p. 272