Which characteristics are common to the three isotopes of hydrogen?

a: atomic number, atomic mass, and electron number
b: atomic mass, electron number, and number of neutrons
c: electron number, number of neutrons, and chemical properties
d: atomic number, electron number, and chemical properties

D should be the correct answer.  isotopes are atoms that have the same atomic number (number of protons) but different atomic masses (number of protons and neutrons).  isotopes also have the same number of electrons since atoms need to have equal numbers of protons and electrons to not be considered ions.  Since the number of protons determines the chemical properties of the atom, we can say that all isotopes have the same chemical properties due to the fact that all isotopes have the same atomic number.

I hope this helps.  Let me know in the comments if anything is unclear.