后天就要考试了，有几道不太清楚，求教一下大家，多谢！

SAS Adv 130 A00-212里面的

第23题

Given the SAS data set ONE:

Group SUM
  A   765
  B   123
  C   564
The following SAS program is submitted:
data_null_;
set one;
call symput(GROUP, SUM)
stop;
run;

What is the result when the program finishes execution?
A.  Macro variable A has a value of 765
B.  Macro variable C has a value of 564
C. Macro variable GROUP has a value of 564
D. Macro variable GROUP has a value of SUM.

不明白为啥答案选A， 请大家帮忙解释一下。