The octahedral complex $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5{\mathrm{SO}}_4\right]\mathrm{Cl}$ exists in two isomeric forms $\mathrm{X}$ and $\mathrm{Y}$. Isomer $\mathrm{X}$ reacts with ${\mathrm{AgNO}}_3$ to give a white precipitate, but does not react with ${\mathrm{BaCl}}_2$. Isomer $\mathrm{Y}$ gives white precipitate with ${\mathrm{BaCl}}_2$ but does not react with ${\mathrm{AgNO}}_3$

• Correct answer
  A

  ionisation isomers
• B

  linkage isomers
• C

  coordination isomers
• D

  solvate isomers

Hence, the correct answer is option: 'A'.