Which of these mixtures are heterogeneous? check all that apply?

There are choices for this question namely:

a. Oil and water

b. Salt and water

c. Brass (and alloy of copper and zinc)

d. Granite (a type of rock with multicolor spots)

The correct answers are oil and water, and granite. Heterogenous mixtures are mixtures wherein the solutes can still be identified from each other. Homogenous mixtures are mixtures wherein solutes are completely mixed and cannot be identified. In oil and water, one can identify which is the oil and which is the water. In granite, it is a mixture of different rocks and these different materials can be identified due to the presence of multicolored spots.