Structures enabling geometric and stereoisomerism

Steps:

• Identify cis-trans isomerism: requires double bond, ring, or coordination with restricted rotation.
• Identify optical isomerism: requires chiral center or asymmetry without plane of symmetry.
• Examine each choice for both features simultaneously.
• Select compound with dual capabilities.

Why B is correct:

• B (trans-1,2-dimethylcyclopropane) has ring-induced cis-trans isomers; trans form lacks symmetry plane, enabling optical activity via enantiomers.

Why the others are wrong:

• A (but-2-ene): Shows cis-trans but no chiral center for optical isomerism.
• C (2-chlorobutane): Has chiral center for optical but no restricted rotation for cis-trans.
• D ([Co(NH3)4Cl2]+): Shows cis-trans but cis is achiral, trans symmetric, no optical.

Final answer: B