The answer is (c).
Ice and air are homogeneous in nature as their particles are not distinctly visible. A homogeneous mixture has a uniform composition throughout its mass. It has no visible boundaries of separation between its various constituents, e.g., air, sugar solution, brass, etc.
A heterogeneous mixture does not have a uniform composition throughout its mass.It has visible boundaries of separation between its various constituents, e.g., soil, wood, blood etc.