In the Current Picture of Earth's Interior, How Is Temperature

In the current picture of Earth's interior, how is temperature thought to change with depth?

A) There is a steady increase of temperature with depth.
B) There is a structure of several layers similar to Earth's atmosphere in which temperature first increases with depth and then decreases and then reverses several more times.
C) The temperature rises only slightly through the mantle, then soars as the core is approached.
D) There is a layer of radioactive materials at the base of the mantle. The temperature increases slowly as one approaches this layer, then it rises sharply through this layer, and then it rises slowly again below this layer.