d
$R \propto l$
Hence every new piece will have a resistance $\frac{R}{{10}}.$
If two pieces are connected in series, then their resistance $ = \frac{{2R}}{{10}} = \frac{R}{5}$
If $5$ such combinations are joined in parallel, then net resistance $ = \frac{R}{{5 \times 5}} = \frac{R}{{25}}$