The standard reduction electrode potentials of four metal cations are:

$E^\circ_{A^+/A} = -0.250\,\text{V}$, $E^\circ_{B^+/B} = -0.140\,\text{V}$,

$E^\circ_{C^+/C} = -0.126\,\text{V}$, $E^\circ_{D^+/D} = -0.402\,\text{V}$

The metal that displaces $A^+$ from its aqueous solution is: