There would be 0 Potential energy, which eliminates A. There would be Spring energy, which eliminates C. So B and D are your 2 choices. Since the child is not moving just before the jump, there would be 0 Kinetic energy. So D.
"M" I believe is the symbol for molarity.
Atomic mass is the number that you get when the protons and neutrons in the nucleus are added together atomic number is the number of protons in the nucleus
