A glass vessel in the shape of a triangular prism is filled with water, and light is incident normally on the face xy. If the refractive indices for water and glass are `4//3` and `3//2` respectively, total internal reflection will occur a the glass-air surface xz only for `sin theta` greater than
A `1//2` , B `2//3`
C `3//4` , D `8//9`
E `16//27`