Answer:
C
Explanation:
Answer A: A surface wave is a wave that travels along the surface of a medium.
Answer B, C: Electromagnetic waves are waves that have no medium to travel whereas mechanical waves need a medium for its transmission.
Answer D: The sentence in the answer D does not fit to the blank in the definition ( of the question )
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Hope this answer can help you.
Answer:
Distance travelled is 7 meters and the displacement is 3 meters
It is by gaining! I just learned this in school. Hope this helps:)