Many Economically Important Metallic Elements Like Gold and Silver Are

Multiple Choice

Many economically important metallic elements like gold and silver are disseminated throughout magma. Why are we able to mine these metals?

A) They are easy to pick out of lava flows with tools that reach a few meters away.
B) They don't melt; they float in lava flows and are then trapped when the lava melts; humans go in and mine the lava flows.
C) They become concentrated by fractional crystallization into the last bit of the magma that remains after most of the silicate minerals have formed.
D) They float up to the surface of the lava and harden on top of the flow.