Which of the following substances cannot be separated? O homogeneous mixture
heterogeneous mixture
element
O compound

Elements.

Explanation: Homogeneous and heterogeneous is just if a mixture is uniform or not. Mixtures and always be separated. Compounds are elements that combined which can be broken down again. So I say the logical answer is an element since it's pure and cannot be broken down into other elements or more of it's self.

i have no clue hope you find the answer

answerleaving cheese out to get moldy;