Question

how earthquakes show us the inside of the earth
scienceprimer
multiple - choice question
p and s waves refract, or bend with a curve, rather than a straight line because
changes in density are rapid
changes in density are slow
density does not change
rewatch

Explanation:

When there are slow changes in density, waves (like P and S waves) refract in a curved path. If density changes were rapid, the refraction would be more like a sharp - angled bend (not a smooth curve). And if density didn't change, there would be no refraction (waves would travel in a straight line).

Answer:

changes in density are slow