a
The forces acting on the ice must balance each other.
Hence buoyant force acting upwards = Weight of the ice
$\Longrightarrow V_{i m m} \rho g=V d g$
$\Longrightarrow \frac{V_{i m m}}{V}=\frac{d}{\rho}=0.9$
Hence, fraction of ice outside water $=1-0.9=0.1$
$=0.1\times 100\%=10\%$