Which of the following is a valid way of putting a tablespace named DAVE_TBS into hot backup mode?

Which of the following is a valid way of putting a tablespace named DAVE_TBS into hot backup
mode?

A.
alter tablespace DAVE_TBS backup mode;

B.
alter tablespace DAVE_TBS start backup;

C.
alter tablespace DAVE_TBS begin backup;

D.
alter tablespace DAVE_TBS backup begin;

E.
alter tablespace DAVE_TBS backup;