In the experiment to find the refractive index of the material of prism. by minimum deviation method $D_m$ the minimum deviation is observed from the graph plotted in the experiment . The graph is plotted between

Question

$(a)\;\text{incident angle and emergent angle} \\(b)\;\text{incident angle and angle of prism.} \\(c)\;\text{angle of deviation and emergent angle.} \\(d)\;\text{incident angle and angle of deviation.}$