Geologists Land on a New Planet and Begin a Series

Geologists land on a new planet and begin a series of seismic measurements. A quake occurs, and they detect both S and P waves on the opposite side of the planet from the quake. What does this say about the planet's geology?

A) There must be large liquid oceans beneath the crust.
B) The structure is much like Earth, with a solid inner core surrounded by a liquid outer core.
C) The entire core must be liquid.
D) The entire core must be solid.