<em>Gravity has the same role as it does in any solar system it keeps the planets in order</em>
I would go with D, because acid can be reduced by using it less
Earthquakes produce P and S waves. The P waves are fast and of a higher frequency than S waves. P waves reach a point first and can pass through liquid media while S waves reach after and the lose much of their energy while passing liquid media. This is because S-waves are shear waves and require rigid/inelastic media for transmission.
During an earthquake, there is usually a shadow zone (where there is no destruction because S-waves did not reach) formed right above the epicenter of the earthquake. This is due to the fact that the S-waves were unable to transit through the liquid inner core of the earth before reaching the earth's surface. Only P-waves are registered in this shadow zone.
Piedmont, Genoa and Nice came to be united
