Answer:
Water and sand
Step-by-step explanation:
the prefix hetero- means 'different' so a heterogeneous mixture would be a mixture in which you can clearly see all of the components.
(like a salad)
sugar and baking soda would dissolve in the water (that would be an example of a homogeneous mixture, the prefix homo- means 'same' homogeneous mixtures have a uniform appearance throughout)
However the sand will definitely not dissolve in the water, it will simply sink to the bottom, and stay there. you would clearly be able to see both the water and the sand.
So the answer can be, none other than
Water and sand.