Earth's layers formed as result of differentiation. during differentiation, different zones of elements form layers and today we know these layers are made up of different elements. certain elements sunk to the center while others collected near the surface. we might predict that the elements, like iron and nickel, formed the core.
a) heavier
b) least dense
c) light weight
d) first crystallized

The closest to the real answer is A, but the real answer is more dense.

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods

myth. it was once thought that animals, including cats and dogs, could only see in black and white. however, scientists have proven this to be a myth. in all animals, including humans, the perception of colour is determined by the presence of cells in the eye called cone photoreceptors.