A: This statement is false. You cannot add a foreign key to a global temporary table because the data in a global temporary table is session-specific, while a foreign key constraint implies a permanent relationship.
B: This statement is false. The ON COMMIT PRESERVE ROWS clause specifies that the data in the table should be preserved until the end of the session, not deleted at the end of the transaction.
C: This statement is false. You can drop a global temporary table without truncating it first.
D: This statement is true. You can alter a global temporary table to add columns within a session.
E: This statement is false. Data in a global temporary table with the ON COMMIT PRESERVE ROWS clause is private to the session that inserted the data, and cannot be seen by other sessions.