1. describe the vibration caused by primary waves. 2. described the vibration caused by secondary waves.

Energy released during an earthquake travels in the form of waves around the Earth. Two types of seismic wave exist, P- and S-waves. They are different in the way that they travel through the Earth. ... They are transverse waves which mean the vibrations are at right angles to the direction of travel.

Independent variable is something that is changed in a experiment. 

Answer sample (c); // would be best because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest;