Which SQL set operator completes the program and generates the desired output?

Given the SAS date sets CLASS1 and CLASS2

CLASS1 CLASS2

NAME COURSE NAME COURSE

Lauren MATH1 Smith MATH2

Patel MATH1 Farmer MATH2

Chang MATH1 Patel MATH2

Chang MATH3 Hiller MATH2

The following SAS program is submitted:

Proc sql;

Select name from CLASS1

<insert SQL set operator here>

select name from CLASS;

quit;

The following output is desired

NAME

Chang

Chang

Lauren

Which SQL set operator completes the program and generates the desired output?
A . UNION ALL
B . EXCEPT ALL
C . INTERSECT ALL
D . OUTER UNION ALL