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"

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.