Which of the following is a characteristic of early paleocene mammals?

1.specialized teeth
2.specialized limbs
3.low brain-to-mass ratios
4.all of the above

Both 1 and 2 are correct so that only leaves me with 4. All of the above

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass