Breeding of individuals that have genes for two different characteristics

dihybrid cross i think would be the best answer for this question 

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

C- a hypothesis or d- an observation