When acetone is added in a two layer mixture of methyl isobutyl ketone and water at $30$C$,$ the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system,

As the acetone concentration increases, the solubility curves approach each other

Both the phases become identical at a particular common point on both the solubility curves called the plait point

The distribution curve which is a plot between x $($acetone concentration in one phase$)$ and y $($acetone concentration in other phase$)$ is analogous to x$-$y curve used in distillation and absorption terminates on the x $=$ y diagonal at the concentration of the plait point

All $($A$),($B$)$ and $($C$)$