In a particular isomer of ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]}^0,\text{ the }\mathrm{Cl}-\mathrm{Co}-\mathrm{Cl}$ angle is ${90}^o$, the isomer is known as 

• A

  optical isomer

• B

  cis-isomer

• C

  position isomer

• D

  linkage isomer