Answer:
Rotation
Step-by-step explanation:
A transformation of a triangle can be either dilation or reflection or rotation or a translation.
Dilation happens when a symmetric figure is formed with scale factor other than 1. But here both triangles have same side length. Hence no dilation
Reflection happens when it is reflected over a line as we see in a mirror. But here the two triangles are not looking as images on a line. Hence no reflection
Rotation is keeping the same shape but rotating through a certain angle. Here DEF is rotated without disturbing its shape or size through a certain angle. Hence rotation is right
Translation is not right because there is no vertical or horizontal shift to get new triangle.
