The reagent used for the detection of $Ni^{2+}$ is $A$. $x$ moles of $A$ react with $Ni^{2+}$ to form a complex of $C$ color. $A$,$x$,and $C$ are respectively:

• A
  $DMG$,$1$,Blue
• B
  $DMG$,$2$,Red
• C
  $EDTA$,$1$,Green
• D
  $EDTA$,$2$,Yellow