Answer:B Protons and Neutrons
Step-by-step explanation:
The nucleus of the atom discovered in 1911 by Ernest Rutherford from the Geiger–Marsden gold foil experiment consists of protons and neutrons at the center of the atom which are are bound together by a nuclear force.
The nucleus has two basic properties which are the mass and charge of which the proton is positively charged having +1 and the neutron having a neutral charge at zero . Both are denoted with mathematical numbers: Z- proton and N-neutron and their addition gives the mass number,A.
Both protons and neutrons have a mass of 1 amu.