In β-E₂ elimination, the number of structural isomers depends on the number of unique β-hydrogens available for removal. Each unique β-carbon can lead to a different alkene isomer.

For the first compound (1-Bromo-1-methylcyclopentane), there are no β-hydrogens, so it gives zero isomers.

The second compound (2-Bromo-3-methylbutane) has two types of β-hydrogens, producing two isomers.

The third compound (2-Bromo-2,3-dimethylbutane) has one type of β-hydrogen, giving one isomer.

The fourth compound (1-Bromo-2,2-dimethylpropane) has three equivalent β-carbons, but each has identical hydrogens, so only one isomer is formed.

Therefore, the correct matching is: (a)-(ii), (b)-(iv), (c)-(iii), (d)-(iii). The final answer is option (c).