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

Case 2-2
Rosalind wants to add attribute declarations to her DTD, and she turns to you for information about the possible attribute types.
-You help Rosalind write the declaration of an attribute named "credits" of an element named "course." This optional attribute should contain character data, and a value of 4 should be used if an attribute value is not specified. Which of the following is an appropriate declaration of this attribute?

A) <!ATTLIST credits course CDATA default="4">
B) <!ATTLIST course credits CDATA default="4">
C) <!ATTLIST credits course CDATA "4">
D) <!ATTLIST course credits CDATA "4">