Which program creates this output?
A. proc freq data = test;
        tables gender*answer/nocol norow nopercent;
    run;
B. proc freq data = test;
        tables answer*gender/nocol norow nopercent;
    run;
C. proc freq data = test;
        tables gender*answer/nocol norow nopercent missing;
    run;
D.proc freq data = test;
        tables answer*gender/nocol norow nopercent missing;
    run;
答案是A为什么不是C呢？明明表格下方有对Frequency Missing=4的统计呢？