Consider the entity-relation (ER) diagram shown in the exhibit.

When the logical database design phase is completed, which of the following is a valid DBDL description of the base relations for the ER diagram?

A.
STUDENT(
Student_Number: integer NOT NULL
Name: variable length character string length 20 NOT NULL)
Primary Key Student_Number
CLASS(
Class_Num: integer NOT NULL
Class_Name: integer NOT NULL)
Primary Key Class_Num

B.
STUDENT(
Student_Number: integer NOT NULL
Name: variable length character string length 20 NOT NULL)
Primary Key Student_Number
CLASS(
Class_Num: integer NOT NULL
Class_Name: integer NOT NULL)
Primary Key Class_Num
Foreign Key Class_Num References STUDENT

C.
STUDENT(
Student_Number: integer NOT NULL
Name: variable length character string length 20 NOT NULL)
Primary Key Student_Number
STU_CLASS(
Student_Number: integer NOT NULL
Class_Num: integer NOT NULL)
Primary Key Student_Number
CLASS(
Class_Num: integer NOT NULL
Class_Name: integer NOT NULL)
Primary Key Class_Num

D.
STUDENT(
Student_Number: integer NOT NULL
Name: variable length character string length 20 NOT NULL)
Primary Key Student_Number
STU_CLASS(
Student_Number: integer NOT NULL
Class_Num: integer NOT NULL)
Primary Key Student_Number, Class_Num
CLASS(
Class_Num: integer NOT NULL
Class_Name: integer NOT NULL)
Primary Key Class_Num