In Huygens principle, the wave theory was established by assuming that the waves were longitudinal. So, option (a) is not correct.
In Maxwell's theory of light, he stated that light is a transverse wave and conducted various experiments to prove so. Hence, option (b) is correct.
Thomas Young conducted his double slit experiment for determining fringe width and tried to prove the wave nature of light by providing that light undergoes interference which is a phenomenon showed by waves. He never proved the type of wave light is, i.e. transverse or longitudinal. Hence, option (c) is not correct.
These statements mostly highlight the wave nature of light. They do not comment on the particle nature of light or the dual nature of light established. Hence, they clearly do not answer the question "what is light" correctly. Hence, option (d) is not correct.