Why does the difference in arrival times of p and s waves increase at seismograph recording stations that are farther away from the epicenter?

This difference increases because p-waves travel faster than s-waves. Therefore, if a seismograph is far from the epicenter, readings of the p-waves will arrive first, but since those waves travel faster than s-waves, it might be a bit longer before readings of the s-waves appear. 

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

Iknow what you are working on the correct answer is c