c
(c)
Breaking stress $=\rho \times g \times L$
Substitute values from the question
Breaking stress $=7.5 \times 10^7 \,Nm ^{-2}$
$\left\{\begin{array}{l}\rho=\text { Density of material } \\ g=\text { Acceleration due to gravity } \\ L=\text { Length of wire that can hang without breaking }\end{array}\right\}$
$\rho=2.7 \times 10^3 \,kg m ^{-3}$
$g=9.8 \,m / s$
$7.5 \times 10^7=2.7 \times 10^3 \times 9.8 \times L$