Which program was used to prepare the data for this PROC PRINT output?

Given the following data set:

Which program was used to prepare the data for this PROC PRINT output?
A . proc sort data=one out=two; by subjid; run;
B . proc sort data=one out=two nodupkey; by subjid; run;
C . proc sort data=one out=two nodup; by subjid; run;
D . proc sort data=one out=two nodupkey; by subjid trt;

Answer: B