Which of these waves moves the fastest?
a. sound
b. radio
c. ocean
d. seismic

First of all, the question is vague as you haven't mentioned the medium of propagation of the wave, which is extremely crucial.

For example light travels at 299,792 km/second in vacuum, but in certain semiconductors, it travels as slow as 9 km/second. Sound, ocean and seismic waves don't exist in vacuum at all.

If you mean the maximum possible speed any of these options can attain in any medium of choice for the different options, then the answer would be 
b. radio waves, which travel exactly at the speed of light in vacuum (299,792 km/second) and with an almost similar(slightly less) speed in air. (Radio waves are nothing but electromagnetic waves with low frequency)

The fastest wave is Radio wave.

Answer is B.

Hope it helps!