Question

1. why do p-waves slow down as they encounter the liquid outer core of the earth?

the liquid outer core is less rigid than the mantle.
the liquid outer core is more rigid than the mantle.
the liquid outer core has more space than the mantle.

Explanation:

P-waves (primary waves) are longitudinal seismic waves whose speed depends on the rigidity of the medium. The mantle is a solid layer with higher rigidity, while the outer core is liquid and less rigid. Lower rigidity reduces the speed of P-waves.

Answer:

The liquid outer core is less rigid than the mantle.