First and second type --- b,b can be adjacent (cis) or diagonal (trans)

third and fourth type --- b,b can be adjacent (cis) or diagonal (trans)

fifth type --- b,c can be adjacent (cis) or diagonal (trans)

sixth type --- b,c can be adjacent (cis) or diagonal (trans)

All complexes here can show geometrical isomerism.

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^{+},

^{3-},

^{+},

^{–},

^{2+} and

^{2+}],

**The number of complex ion(s) that show(s) cis-trans isomerism is(are).**