You are a database developer. You plan to design a database solution byusing SQL Server 2008. You are creating adataba seto support the office manager. Your database model has the following structure. The database design has the following business requirements: An employee can be assigned more than one task. Upon completion, thetask is deleted. When a task is deleted, the associated assignment is deleted. When an employee is nolonger available tocomple tea task, theemployee link to the assignment is replaced with a NULL value. You need to implement the business requirements to maintain data integrity. What should you do?（）

• A、Create DDL INSERT triggers on the Employee. Task and  Assignment entities.
• B、Create CHECK constraints on the Task  ID and Employee  ID attributes in the  Assignment entity.
• C、Create  Foreign  Keys constraints on  the  Task  ID and  EmployeeID attributes in the  Assignment entity. Reference the Task and  Employee entities respectively. Specify the  appropriate On Delete action.
• D、Create  Foreign  Keys constraints  on  the  Task  ID and  Employee  ID attributes in theTask and  Employeeentities respectively. Reference the  Assignment entity, and specify the  appropriate On Delete action.