If No One Has Ever Visited the Core of the Earth

Multiple Choice

If no one has ever visited the core of the Earth, how do we know that it is made of metals?

A) core material seeps up through volcanoes in the crust
B) circulating liquid metals in the core set up a large (measurable) magnetic field
C) spectroscopy allows us to tell what the core is made of by analyzing the light we receive
D) the amount of radioactivity shows metals must be present; only metals are radioactive
E) you can't fool me; there is NO evidence that the Earth's core has metals