命令sqlplus/nolog的作用是（）

A.LIST EMP

B.DESC EMP

C.SHOW DESC EMP

D.STRUCTURE EMP

E.SHOW STRUCTURE EMP

A. set server on

B. set serverecho on

C. set servershow on

D. set serveroutput on

E. set serverdisplay on

A. write to d:\data1.txt

B. output to d:\data1.txt

C. spool to d:\data1.txt

D. spool on d:\data1.txt

E. spool d:\data1.txt

A.set time on

B.set timing on

C.set long

D.set timelong on

E.set sqlprompt