Young's modulus is defined as the ratio of stress to strain: .

In the given graph, the y -axis represents strain and the x -axis represents stress.
The slope of the line in a strain-stress graph is given by .
Therefore, .
To have the largest Young's modulus, the material must have the smallest slope in the strain-stress plot.
From the figure, line has the smallest angle with the stress axis ( x -axis), meaning it has the minimum slope.
Since , material has the largest Young's modulus.