What difference allows scientists to separate earth into these layers: crust, mantle and core? A. Convection currents
B. Heat flow
C. Chemical composition
D. Physical properties

This type of galaxy is an approximately ellipsoidal shape and a smooth, nearly featureless image. they are the largest single star systems, in the universe and are built by the collisions of many smaller galaxies.

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