You want to be notified when the space usage of an existing critical tablespace has reached 75% of the allocated space. Which option would you use to achieve this？（）

• A、run a procedure to check the tablespace space usage
• B、define the warning threshold for the tablespace at 75% in Database Control
• C、create a trigger to be executed when tablespace space usage reaches 75%
• D、submit a job by using DBMS_JOB package to check the free space in the tablespace at regular intervals
• E、define the warning threshold to be 75% for the tablespace by ALTER TABLESPACE .. ADD THRESHOLD command