Which of these mixtures are heterogeneous? a. oil and water b. salt and water c. brass (an alloy of copper and zinc) d. granite

The mixture that has been heterogeneous has been oil and water. Thus, option A is correct.

The mixture has been defined as the combination of two or more substances. The mixture has been categorized as pure and heterogeneous mixture based on the solubility of the constituents.

The pure mixture has been defined as the one in which the constituent substances are completely soluble, and are not visible with the bare eyes.

The heterogeneous mixture has been defined as the combination in which the constituents elements are not completely soluble and are easily differentiated from each other by physical means.

Thus, the mixture that has been heterogeneous has been oil and water. Thus, option A is correct.

Learn more about heterogeneous mixture, here:
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The correct answer would be A, oil, and water

Explanation:

Water and oil are considered a heterogeneous mixture because it's a composition that has two or more phases meaning they could be separated if need be. I hope this helps :)