Answer:
<u>Earth's</u><u> </u><u>plates</u><u> </u><u>moving</u><u> </u><u>&</u><u> </u><u>colliding</u><u> </u><u>against</u><u> </u><u>one</u><u> </u><u>another</u><u>.</u>
The last one
Explanation:
I have done this before
Nice experiment
it increases and is perpendicular to the motion of the wave.
