Consider the following reduction processes:
$Al^{3+} + 3e^{-} \rightarrow Al_{(s)}, E^{\circ} = -1.66 \ V$
$Fe^{3+} + e^{-} \rightarrow Fe^{2+}, E^{\circ} = +0.77 \ V$
$Co^{3+} + e^{-} \rightarrow Co^{2+}, E^{\circ} = +1.81 \ V$
$Cr^{3+} + 3e^{-} \rightarrow Cr_{(s)}, E^{\circ} = -0.74 \ V$
The tendency to act as a reducing agent decreases in the order:

• A
  $Al > Cr > Fe^{2+} > Co^{2+}$
• B
  $Al > Fe^{2+} > Cr > Co^{2+}$
• C
  $Al > Cr > Co^{2+} > Fe^{2+}$
• D
  $Cr > Fe^{2+} > Al > Co^{2+}$