The diagram below shows four layers of Earth.

The picture shows the internal structure of Earth. The central region is labeled 'A.' The layer around the central region is labeled 'B.' The outermost layer is labeled 'D.' The layer inside Earth which is just after layer D is labeled 'C.'

Which layers of Earth consist mainly of silicates and magnesium oxide?

Layer A and B
Layer B and C
Layer C and D
Layer D and A