Crossing over happens during a. anaphase 1. b. metaphase 1. c. any phase in meiosis. d. prophase 1.

D. Prophase1 because this has to happen first so the rest of the stages can continue with their own events 

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