The technology of sesimograph is helpful to humans because it

Explanation:

Seismographs can detect quakes that are too small for humans to feel. During an earthquake, ground-shaking seismic waves radiate outward from the quake source, called the epicenter. Different types of seismic waves travel at different speeds and through different parts of the Earth during a quake.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.