#### Answer

The slope between $(1,3)$ and $(2,1)$
$\frac{1-3}{2-1}=\frac{-2}{1}=-2$
The slope between $(-4,0)$ and $(-3,-2)$
$\frac{-2-0}{-3-(-4)}=\frac{-2}{1}=-2$
Two sides have the same slope, so these two sides are parallel. These sides are also opposite sides. So this is a parallelogram.

#### Work Step by Step

See "answer".