How do you separate a mixture of wheat, sand and husk?

What is the principle used in the separation of mixtures? In which of the separation methods we use:

$\left(\mathrm{a}\right)$ Wind     $\left(\mathrm{b}\right)$ Churner     $\left(\mathrm{c}\right)$ Water     $\left(\mathrm{d}\right)$ Strainer

The flow diagram shows the steps involved in the separation of a mixture of sand and sugar. Observe it and fill in the blanks at $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$.

Differentiate between:

Homogeneous and heterogeneous substances