Which is a longitudinal wave that requires a medium to move? sound wave ocean wave lightwave radio wave microwave
You are looking for what are called mechanical waves. The other class of waves are called electromagnetic waves. A key characteristic of electromagnetic waves is that they can travel through a vacuum. So pick out the electromagnetic waves and you are on your way. However there is a complication which is described here: http://www.physicsclassroom.com/class/waves/Lesson-1/Categories-of-Waves It all boils down to what is meant by an ocean wave. Over to you and your Physics notebook/textbook.
On reading the question again, since it asks for a (=one?) longitudinal wave there is only one answer.
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