Which of the following is a geneous mixture?

Salt water. Every drop of the slat water looks just like every other drop in the sample. That is not true of the other three examples. In each of the other three it is easy to imagine grabbing a spoonful that looks very different from another spoonful of the same mix (all sand, and little water then mostly water, potatoes first then meat, small pebble mix followed by a sandy mix).