The stress-strain curves are drawn for two different materials X...

$$\text{ The stress-strain curve for a material is shown }$$
$$\text{ This curve specifies the behaviour of material. }$$ For the material, if distance between strength point and fracture point is small, so it is brittle and will break easily on the application of some extra stress after point D. For material $\mathrm{Y}$, if the distance between strength point and fracture point is large, so it is a ductile material and can withstand for some extra stress beyond point $\mathrm{D}$.