To solve this problem, we will first review what each of the transformations looks like.
a dilation is a scaling of a figure. So basically we take one figure and then stretch it or contract it. We can tell that a dilation was applied if the length of the sides of a figure (if it has any) are different.
In this case, we can see that both triangles 1 and 3 have the same side lengths. So no dilation was applied.
a reflection is a transformation where we "mirror" a figure with respect to a line. We can tell that a reflection was applied if the orientation of the figures are different.
In this case, we can see that both triangles 1 and 3 have the same orientation. Meaning that they "look they same". So no reflection was applied.
a rotation is a transformation where we spin the figure with respect to a fixed point. This transformation also changes the orientation of the figure.
As in this case, both triangles have the same orientation, this means that no rotation was applied.
a translation consists of moving a figure around, without rotating it or dilating it.
As in this case triangle 3 has the same orientation and lengths as triangle 1, but is located somewhere else, it means that a translation was applied to triangle 1 to get triangle 3