Case 2-2 Rosalind Wants to Add Attribute Declarations to Her DTD, and DTD

Multiple Choice

Case 2-2
Rosalind wants to add attribute declarations to her DTD, and she turns to you for information about the possible attribute types.
-Rosalind wants to declare a "coursenum" attribute, the values of which will be unique within the document. Which attribute type should she use?

A) CDATA
B) UNIQUE
C) ID
D) IDREF