Consider the following (normalized) relational model (primary keys are underlined, foreign keys are in italics). EMPLOYEE(SSN, ENAME,

Consider the following (normalized) relational model (primary keys are underlined, foreign keys are in italics).

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EMPLOYEE(SSN, ENAME, EADDRESS, SEX, DATE OF BIRTH, SUPERVISOR, DNR) SUPERVISOR: foreign key refers to SSN in EMPLOYEE, NULL value allowed DNR: foreign key refers to DNR in DEPARTMENT, NULL value not allowed DEPARTMENT(DNR, DNAME, DLOCATION, MGNR) MGNR: foreign key refers to SSN in EMPLOYEE, NULL value not allowed PROJECT(PNR, PNAME, PDURATION, DNR) DNR: foreign key refers to DNR in DEPARTMENT, NULL value not allowed WORKS_ON(SSN, PNR, HOURS) SSN: foreign key refers to SSN in EMPLOYEE, NULL value not allowed PNR: foreign key refers to PNR in PROJECT, NULL value not allowed Which statement is correct? a. According to the model, a supervisor cannot supervise more than one employee. b. According to the model, an employee can manage multiple departments. c. According to the model, an employee can work in multiple departments. d. According to the model, an employee should always work on projects assigned to his/her department.