多项选择题 YouworkasadatabaseadministratorforCertkiller.com.Oneofthedatabaseusersaccidentallydeletedalltherowsofacriticaltableandcommittedthedeleteat1：30p.m.Youseniordatabaseadministrator，Certkiller，asksyoutoretrievethelostdata.Whichtwoactionswouldyouusetoensurethatthereisnoimpactonotherconnecteduserswhileretrievingthedeletedrows？（）

单项选择题 You work as a database administrator for Certkiller .com. When you tried to connect to the database， you received the following error： ERROR：  ORA-12541：TNS：no_listener  You found that the listener is not running on the server， so you issued the following command in the Listener Control utility to start the listener.  lsnrctl>START  What statement is true？（）

单项选择题 You execute the following command in your Certkiller .com production database to change the width of the CUST_NAME column of the CUSTOMERS table： ALTER TABLE customers  MODIFY （cust_nameVARCHAR2 （40）） /  When you execute the command， it displays the following error message：  ERROR at line 1：  ORA-00054： resource busy and acquire with NOWAIT specified  What could be the reason for the error message？（）