If the SQL Statement SELECT C1,C2,C3

Multiple Choice

If the SQL statement SELECT C1,C2,C3
FROM T4
WHERE C2 = 'Smith';
Is frequently executed,which column(s) should be considered for indexing based only on the statement itself?

A) C1 only
B) C2 only
C) C3 only
D) C1 and C2
E) C1,C2,and C3