$[Co(en)_3]^{3+}$ ion is expected to show

• A
  two optically active isomers: $d$ and $l$ forms
• B
  three optically active isomers: $d, l$ and meso forms
• C
  four optically active isomers: cis,$d$ and $l$ isomers and trans $d$ and $l$ isomers
• D
  none of these