One Would Expect a Fairly Even Distribution of Elements on the Earth;

One would expect a fairly even distribution of elements on the earth; instead, the distribution is uneven. Which of the following best describes why we observe this?

A) The nebula that formed the earth had elements that were not evenly distributed.
B) Winds on the surface of the earth have moved the heavy and light elements into bands.
C) The early earth liquefied, resulting in heavier elements migrating toward the core and lighter elements moving toward the surface. This migration to the surface was largely by lava flows, which were inconsistent.
D) Some water-soluble elements were washed by water into pockets on the surface.
E) The magnetic properties of the core caused the metals to pool into certain areas between the poles on the earth.