<insert By statement here?

Given the non-indexed SAS data set TEMP:

TEMP

X Y

P 52

P 45

A 13

A 56

R 34

R 12

R 78

The following SAS program is submitted:

Proc print data=temp;

<insert By statement here?

Run;

Which by statement completes the program, create a listing report that is grouped by X and completes without errors?
A . X;
B . By X groupd;
C . By X notsorted;
D . By descending X;