The main organs of the excretory system are the
large intestine and rectum
skin and kidneys
urinary bladder and skin
heart and kidneys

As weird as it may seem, its actually the skin and kidneys! the skin plays an important role with removing toxins from the body through sweat ect. and the kidneys work to neutralise toxins and break down liquids in the body, so that they can then be removed from the system and released through the body in the excretory system. 

Writing, you can revisit previous parts of the lesson by returning to the course map. be sure to refer to the lab’s student guide, which you can find on the first page of the lab experiment activity

What is the question? if you were looking to design a method of separating something, you can separate this compound by putting both in water and allowing the water to dissolve the sugar. then pour it into another beaker and evaporate it then boom! salt and sugar : )