Which choice best describes why a solution is called a special type of mixture? The substances in a solution can only be separated through the method called filtration. The substances in a solution look as if they mixed equally but they always separate into layers when left sitting still a long time. The substances in a solution are mixed equally throughout it and are unable to be easily separated like those in a regular mixture. The substances in a solution are mixed unequally but they can still easily be separated just like those in a regular mixture.