A.atomic mass(a)=16
atomic mass(b)=18
b.a and b are isotopes
c.(a)=2,6
(b)=2,6
Solar Energy is the answer
D. the potential energy of the reactants is low; the potential energy decreases gradually; then increases slightly.
I believe it is B. A series circuit has one path for electrons, but a parallel circuit has more then one path.
Could I Have brainliest?