Question

Which of the following is a type of wave that does not need a medium though which to travel?

Equilibrium

Longitudinal

Amplitude

Transverse

Answer 1

I think number D is the answer  

Answer 2

I'm pretty sure the answer is A. I am taking the test right now and that seems to be the only logical answer.

I will update if I get it correct.

So I got it wrong :( it is not A or D. My next thought would be C though