The Graph Below Shows the Change in Velocity of Seismic

The graph below shows the change in velocity of seismic waves with depth in the crust.Why does the velocity of the P-wave drop drastically at the core-mantle boundary?

A) because the core is much denser than the mantle
B) because the outer core is solid and P-waves can't pass through solids
C) because the outer core is liquid and seismic waves travel slower in liquids
D) because the S-waves are removed and that energy is transferred to the P-waves