Which three statements are true about the DESCRIBE command? (Choose three.)

A. It can be used only from SQL*Plus

B. It can be used to display the structure of an existing view

C. It can be used from SQL Developer

D. It displays all constraints that are defined for each column

E. It displays the PRIMARY KEY constraint for any column or columns that have that constraint

F. It displays the NOT NULL constraint for any columns that have that constraint