Samples of four metals $A$, $B$, $C$ and $D$ were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

Metal	Iron $(II)$ sulphate	Cooper $(II)$ sulphate	zinc sulphate	Silver nitrate
$A.$	No reaction	Displacement
$B.$	Displacement		No reaction
$C.$	No reaction	No reaction	No reaction	Displacement
$D.$	No reaction	No reaction	No reaction	No reaction

Use the Table above to answer the following questions about metals  $A$, $B$, $C$ and $D$.

$(i)$ Which is the most reactive metal ?

$(ii)$ What would you observe if $B$ is added to a solution of Copper $(II)$ sulphate ?

$(iii)$ Arrange the metals $A$, $B$, $C$ and $D$ in the order of decreasing reactivity.

$A + FeSO _{4} \rightarrow$ No reaction, i.e., $A$ is less reactive than iron

$A + CuSO _{4} \rightarrow$ Displacement, i.e., $A$ is more reactive than copper

$B + FeSO _{4} \rightarrow$ Displacement, i.e., $B$ is more reactive than iron

$B + ZnSO _{4} \rightarrow$ No reaction, i.e., $B$ is less reactive than zinc

$C + FeSO _{4} \rightarrow$ No reaction, i.e., $C$ is less reactive than iron

$C + CuSO _{4} \rightarrow$ No reaction, i.e., $C$ is less reactive than copper

$C + ZnSO _{4} \rightarrow$ No reaction, i.e., $C$ is less reactive than zinc

$C + AgNO _{3} \rightarrow$ Displacement, i.e., $C$ is more reactive than silver

$D + FeSO _{4} / CuSO _{4} / ZnSO _{4} / AgNO _{3} \rightarrow$ No reaction, i.e.,

$D$ is less reactive than iron, copper, zinc, and silver

From the above equations, we obtain :

$\begin{matrix}
   \begin{matrix}
   \begin{matrix}
   Zn  \\
   B  \\
\end{matrix}  \\
   Fe  \\
   A  \\
   Cu  \\
\end{matrix}  \\
   C  \\
   Ag  \\
   D  \\
\end{matrix}\begin{matrix}
   \begin{matrix}
   \downarrow   \\
   \downarrow   \\
   \downarrow   \\
   \downarrow   \\
\end{matrix}  \\
   \downarrow   \\
   \downarrow   \\
   \downarrow   \\
\end{matrix}\begin{matrix}
   Most\,\,reactive  \\
   reactivity\,\,Series  \\
   Least\,\,reactive  \\
\end{matrix}$

$(i)$ $B$ is the most reactive metal.

$(ii)$ If $B$ is added to a solution of copper $(II)$ sulphate, then it would displace copper.

$B + CuSO _{4} \rightarrow$ Displacement

$(iii)$ The arrangement of the metals in the order of decreasing reactivity is: $B > A > C > D$