we know that
if a dilation produces a smaller figure
then
0< scale factor <1
so
case A) -2------> the scale factor must be a positive number
case B) 1/3----> 0< 1/3 <1---> is a possible scale factor
case C) 1------> this scale factor does not not produce a smaller figure, it produces the same figure
case D) 4----> this scale factor produces a larger figure
the answer is
1/3