It defines the element. If you change the protons, you change the type of element. A proton is positively charged and is most of the mass of the atom, next to the neutron. Neutrons have a very very very slightly higher mass.
Do the atomic mass times the number of atoms you have. That'll give you your answer. Hope it helps!
I think the best answer is B. Even this is the broadest case for the Conservation of matter and the one for Energy, the only way this can be applied is in nuclear rxns.
1.34*10^6
Move the decimal 6 times to the left, it is a number 1-10
