this graphic shows

a
different ions of hydrogen
b
beta decay of hydrogen
c
different isotopes of hydrogen
d
hydrogen becoming a new element

c ) Different isotopes of hydrogen

Explanation: In chemistry, you define an isotope from one element, as the one composed by same number of protons, but different number of neutrons. This difference makes isotopes to have different physical properties

For Hydrogen, you may find 3 isotopes: Hydrogen (which has 1 proton and contains no neutrons), Deuterioum (which contains 1 proton and 1 neutron) and Tritium (which contains 1 proton and 2 neutrons)

Proton is referrenced as "p" and neutron is referrenced as "n"

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )