Answer
a). $(2)$ water to air,
b). $48.8^{\circ}$.
Work Step by Step
a). For total internal reflection to occur, light must go from more optically dense medium to a less optically dense one, it must go from high n-medium into a low n-medium, which is the case for water to air.
So, the answer is (2)
b). From Snell's law,
$sini_{c}=\frac{n_{a}\times sin90^{\circ}}{n_{w}}=\frac{1}{1.33}$
So, $i_{c}=48.8^{\circ}$
