How Does a Seismograph Detect Vibrations from the Passing Wave

Multiple Choice

How does a seismograph detect vibrations from the passing wave front of an earthquake?

A) The wave front seeks out the instrument which stops vibrating when the wave front reaches it.
B) The instrument is anchored to the ground or buried in a vault so that it is stationary with respect to the earth. When the instrument moves, the suspended mass inside is relatively stationary due to inertia. The relative motion registers the quake.
C) The instrument vibrates with the ground as it rolls along a track above the focus.
D) The whole instrument moves up and down (or back and forth) on the ground, so that it starts jiggling a little weight inside that trips the detector to record the earthquake.