Fraction of thickness of ice block out of water is
$x=1-\left(\frac{\rho_{\text {ice }}}{\rho_{\text {water }}}\right)=1-\frac{0.9}{1} \text { or } x=0.1$
So, minimum length of rope required $\approx$ thickness of ice $\times 0.1=8 \times 0.1=0.8 \,m$. Hence, nearest option is $0.9 \,m$.




