c
(c)\(l = \frac{{FL}}{{\pi {r^2}Y}}\)\( \Rightarrow l \propto \frac{L}{{{r^2}}}\) (F and Y are constant) \(\frac{{{l_1}}}{{{l_2}}} = \frac{{{L_1}}}{{{L_2}}}{\left( {\frac{{{r_2}}}{{{r_1}}}} \right)^2} = \frac{1}{2}{\left( {\sqrt 2 } \right)^2}\)
\(\frac{{{l_1}}}{{{l_2}}} = 1:1\)