The Moon is significantly smaller than the Earth and so its core contained less energy to begin with and also cooled significantly faster. Thus, the Moon's core is relatively cool and solid, whereas a portion of the Earth's core is liquid.
A layer of rock might have eroded is an unconformity in a sequence of rock layers that reveal about geologic history. The correct option among all the options that are given in the question is the second option or option "B". I hope that this is the answer that will come to your help.
