Compounds $$\(\mathbf{A}, \mathbf{B}, \mathbf{C}\)$$ and $$\(\mathbf{D}\)$$ all have the molecular formula $$\(\mathrm{C}_{4} \mathrm{H}_{8}\)$$. $$\(\mathbf{A}, \mathbf{B}\)$$ and $$\(\mathbf{C}\)$$ each contain one double bond, but $$\(\mathbf{D}\)$$ does not. $$\(\mathbf{A}\)$$ and $$\(\mathbf{B}\)$$ are geometric isomers of each other. Deduce a possible structure and name for each compound. (4)

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