Which of the Following Best Characterizes How the Diameter of Earth's

Which of the following best characterizes how the diameter of Earth's core and the nature of the outer core were discovered?

A) Crystalline iron was found in lavas erupted from the deepest known hot spots.
B) because P- wave speeds are higher in the outer core than in the lower mantle
C) by analysis of the P- wave and S- wave shadow zones
D) by using the ratio of iron meteorites to stony meteorites to deduce the relative diameters of the core and mantle