1. For a thin prism, the angle of minimum deviation is approximately $D_m \approx (\mu-1)A$ where $\mu$ is the refractive index of the prism material and $A$ is the prism angle.

2. Therefore, for a given prism, $D_m \propto (\mu-1).$ So the variation of $D_m$ with wavelength $\lambda$ will follow the same trend as the variation of refractive index $\mu$ with $\lambda$.

3. For crown glass under normal dispersion, refractive index decreases as wavelength increases: $\lambda \uparrow \;\Rightarrow\; \mu \downarrow$ Hence, $\lambda \uparrow \;\Rightarrow\; D_m \downarrow$

4. Also, since the given $\mu$ vs $\lambda$ graph for crown glass is a decreasing, non-linear curve, the $D_m$ vs $\lambda$ graph will have the same shape, only shifted/scaled because of $D_m=(\mu-1)A.$

5. So the correct graph must be the one in which $D_m$ decreases with increasing wavelength in the same manner as $\mu$ decreases.

Hence, the correct option is A.