Which BY statement completes the program, creates a listing report that is grouped by X and completes without errors?

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, creates a listing report that is grouped by X and completes without errors?
A . By X notsorted;
B . By X grouped;
C . By Descending X;
D . By X;