Which statement is true about aggregate functions?

Which two statements are true about views used for viewing tablespace and datafile information?
(Choose two.)

Examine the description of the BOOKS table:

The table has 100 rows.
Examine this sequence of statements issued in a new session:
INSERT INTO books VALUES ('ADV112', 'Adventures of Tom Sawyer', NULL,
NULL);
SAVEPOINT a;
DELETE FROM books;
ROLLBACK TO SAVEPOINT a;
ROLLBACK;
Which two statements are true? (Choose two.)

Examine the description of the PROMOTIONS table:

You want to display the unique promotion costs in each promotion category.
Which two queries can be used? (Choose two.)

Which two tasks can you perform using DBCA for databases? (Choose two.)