Select the ion.
a) no2
b)h2so4
c) al+3

I believe the correct answer from the choices listed above is the third option. The ion would be Al+3. It is obvious because among the options, this is the only substance that has a charge. An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. 

It conforms what ever surface its in.