The type of seismic waves that arrive at the surface first and move by compressing and expanding the ground like an accordion are called
a. s waves.
b. p waves.
c. surface waves.
d. mercalli waves.

b. P waves

Explanation:

A P-wave is one of the two main types of elastic body waves, called seismic waves in seismology. P-waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P-waves may be transmitted through gases, liquids, or solids. Primary waves are alternatingly compressional and extensional, and cause the rocks they pass through to change in volume. These waves are the fastest traveling seismic waves and can travel through solids, liquids, and gases. Also called P wave. See Note at earthquake. P Waves are compressional which means they move through (compress) a solid or liquid by pushing or pulling similar to the way sound travels through the air. The particles of the material a P Wave pushes through move in the direction of the P wave's energy.

the higher the current the higher the mag field around it the higher the influence on the compass