To obtain the definition of a view, you can query the data dictionary view called USER_VIEWS. This view contains information about all the views owned by the current user.
Option A) Using the DESCRIBE command in the EMP_DEPT_VU view is incorrect. The DESCRIBE command is used to display the structure of a table, not a view.
Option B) Using the DEFINE VIEW command on the EMP_DEPT_VU view is incorrect. The DEFINE VIEW command is not a valid command in most database systems. It is not used to obtain the definition of a view.
Option C) Using the DESCRIBE VIEW command on the EMP_DEPT_VU view is incorrect. The DESCRIBE VIEW command is not a valid command in most database systems. It is not used to obtain the definition of a view.
Option D) Querying the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view is correct. The USER_VIEWS view contains information about all the views owned by the current user, including their definitions.
Therefore, the correct answer is D) Query the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view.