Which of the following is an invalid argument?, homework help

A.  If light is composed only of waves, then light cannot travel across empty space.  But light is composed only of waves, therefore light cannot travel across empty space.

B.  If light is composed only of particles, then light cannot exhibit diffraction patterns; and light is composed only of particles, so light cannot exhibit diffraction patterns.

C.  If light is composed only of waves, then light cannot travel across empty space.  But light can travel across empty space.  Therefore light is not composed only of waves.

D.  If light is composed only of particles, then light cannot exhibit diffraction patterns; and light is not composed only of particles, therefore light can exhibit diffraction patterns.