Suppose an Earthquake Occurs on an Imaginary Planet

Multiple Choice

Suppose an earthquake occurs on an imaginary planet.Scientists on the other side of the planet detect primary waves but not secondary waves after the quake occurs.This suggests that

A) part of the planet's interior is liquid.
B) all of the planet's interior is solid.
C) the planet has an iron core.
D) the planet's interior consists entirely of rocky materials.