The correct increasing order of field strength of ligands based on spectro chemical series is

• A

  ${\mathrm{I}}^{-}, {\mathrm{OH}}^{-}, {\mathrm{CN}}^{-}, {\mathrm{NH}}_3$

• B

  ${\mathrm{OH}}^{-}, {\mathrm{Br}}^{-}, {\mathrm{NO}}_2^{-},{\mathrm{NH}}_3$

• C

  ${\mathrm{F}}^{-}, {\mathrm{SCN}}^{-}, {\mathrm{CN}}^{-}, \mathrm{CO}$

• D

  ${\mathrm{H}}_2\mathrm{O}, {\mathrm{NH}}_3, {\mathrm{CN}}^{-}, \mathrm{CO}$