following tour wires ot length $L$ and raduk are made of the same material. Which of these will have the largest extension, when the same tension is applied?
(a) $L=100 \mathrm{~cm}, r=0.2 \mathrm{~mm}$
(b) $L=200 \mathrm{~cm}, r=0.4 \mathrm{~mm}$
(c) $L=300 \mathrm{~cm}, r=0.6 \mathrm{~mm}$
(d) $L=400 \mathrm{~cm}, r=0.8 \mathrm{~mm}$