Engineering stress vs strain graph

What does the gradient of each line represent

the stiffness or elastic modulus of the material, indicating how much it deforms under stress.

What does the height of the curve represent

The ultimate tensile strength of the material, which is the maximum stress it can withstand before failure.

what does the distance along the x axis represent

The ductility of the material in terms of strain, indicating how much it can deform before fracture.

Material properties of A

High stiffness, moderate to high strength but very low ductility

Material properties of B

Highest strength out of others, high stiffness, low ductility, deforms plastically

Material properties of C

medium strength and stiffness, plastically deforms but has high ductility

Material properties of D

Low strength and stiffness, deforms plastically but has high ductility