What is the purpose of the SQL ROLLBACK statement? $($Check all that correctly describe an aspect of what a standard ROLLBACK statement does.$)$

a$.$

Recover the database from a backup tape.

b$.$

Make any pending changes permanent in the database.

c$.$

End the current transaction.

d$.$

Change existing data in the database.

e$.$

INSERT uncommitted data into the database.

f$.$

Revert any changes made by the transaction to the state when the transaction began.