Which best describes the difference between a seismograph and seismogram?

a. a seismograph is the instrument that detects and records volcanic activity, while a seismogram is the written record of that activity.

b. a seismograph is a written record of volcanic eruptions, while a seismogram is a written record of earthquakes.

c. a seismograph records tectonic activity, while a seismogram records volcanic activity.

d. a seismograph is the instrument that detects and records movements within the earth, while a seismogram is the recording.