Item 47 of 63 Mark item for review  

The following SAS program is submitted:

%macro execute;

     [_insert_statement_here_]  

       proc printdata=SASUSER.HOUSES;  

        run;

     %end;   

%mend execute;

%execute   

Which statement completes the program so     

that the PROC PRINT step executes on Thursday?  

        A.

if &sysday = Thursday then %do;

     B.

%if &sysday = Thursday %then %do;     

     C.

%if "&sysday" = Thursday %then%do;   

     D.

%if &sysday = "Thursday" %then%do;  

这个是b，但是为什么不用加双引号resolve呢？我一直没有把什么时候需要双引号resolve什么时候不需要搞明白