<span>A rigid transformation is a transformation of the plane that preserves length.
Reflections, translations, rotations, and combinations of these three transformations are "rigid transformations".
The transformation

is a transformation where the x-value of the original figure is streched by a factor of 3.
</span>
<span>Therefore, the correct explanation is
The
transformation is a stretch by a factor of
3, so it preserves the length
of
y segments but not the length of
x segments. In order to be a rigid
motion, the transformation must preserve lengths, so this transformation
not
a rigid motion.</span>