oracle数据库中，如何提交事务？（）

A.drop tablespace tablespace_name；
B.drop tablespace tablespace_name including contents；
C.drop tablespace tablespace_name including contents and datafiles；
D.drop tablespace tablespace_name including datafiles；

A.select TABLE_NAME from dba_tablespace where tablespace_name=’表空间名’
B.select TABLE_NAME from dba_tables where tablespace_name=’表空间名’
C.select TABLE_NAME from dba_tables where table_name=’表空间名’
D.select TABLE_NAME from dba_tablesspace where tables_name=’表空间名’

A.exp secnet/secnet FILE={文件名.dmp buffer=2048000TABLES=fenghuo log=（日志文件名）.log DIRECT＝y
B.exp secnet/secnet buffer=2048000file={文件名.dmp tablespaces=fenghuo
C.exp secnet/secnet buffer=2048000file={文件名.dmp owner=fenghuo log=（日志文件名）.log
D.exp system/sys FILE={文件名.dmp buffer=2048000TABLES=fenghuo log=（日志文件名）.log DIRECT＝y