Answer:
The third one.
Explanation:
A dilation is a shrink or a stretch of a figure.
In a dilation, all sides either increase or decrease by the same scale factor. Additionally, in a dilation the angle measures of the figure do not change.
In the first figure, we can see that the base angles of the pre-image are slightly different than those of the image. This is not a dilation.
In the second figure, the angles are noticeably different; again, not a dilation.
In the fourth figure, much like the second figure, the angles are noticeably different. This is not a dilation.
In the third figure, however, we can see that the slanted sides of the larger figure go through three boxes; they are three units long. Additionally we can see that the slanted sides of the smaller figure go through 1 side; this is a dilation b a factor of 3.
The base sides of the third figure, in the larger shape, are 6 units long; in the smaller figure, they are 2 units long. This is a dilation by a factor of 3.