I really don’t know but I think it’s D

A system that can be affected by the outside environment, by an exchange of matter or energy is an open physical system .
<span>Suppose you mixed two chemicals in the lab until you could not tell the two apart. After some time passed, a white powder formed which would not dissolve, and settled on the bottom. The mixture was first homogeneous then heterogeneous. </span>
D. The environment
Is the right answer