An optical bench is used to project real images formed by a thin converging lens of focal length \(f\). The distance \(d_o\) of an illuminated object from the lens is varied across the domain \(d_o > f\), and the corresponding image distance \(d_i\) is measured on a screen. Which of the following best describes the qualitative shape of the graph of image distance \(d_i\) as a function of object distance \(d_o\), and the physical reason for its asymptotic behavior as \(d_o \to \infty\)?