The moon’s average density is about the same as the density of which of the earth’s layers?

Which best describes the nucleus of an atom a. it is where all of the particle s of the atom are located b. it is the negatively charged part of the atom c. it is where the electrons and the protons are located d. it is the part of the atom with the greatest mass

What is the membrane that sheath of schwann cell containing cytoplasm and nucleus that encloses myelin

Can someone give me the answers to this?