Option (2)
Step-by-step explanation:
ΔDEF is a dilation image of ΔABC.
Rule for the dilation,
Scale factor = ![\frac{\text{Length of one side of the image triangle}}{\text{Length of one side of the original triangle}}](/tpl/images/1380/1243/756b6.png)
          = ![\frac{DE}{AB}](/tpl/images/1380/1243/6d2cd.png)
          = ![\frac{4}{8}](/tpl/images/1380/1243/41fc9.png)
          = ![\frac{1}{2}](/tpl/images/1380/1243/9cdae.png)
Therefore, scale factor by which ΔABC is dilated is
.
Option (2) will be the correct option.