[misstear31]

Hi,
I have a mid term exam tomorrow, and I can't answer a question from a previous exam...
Here is the question with formulas :


Text : The four compounds A, B, C and D all have carboxyl group and three of them have an amino group.
You measure the pK values for these 7 group and obtain  the values : 2, 3, 4, 5, 8, 9 and 10.
Which values correspond to which group in A, B, C and D ?

I have looking for an explanation everywhere, you are my last chance.
Thanks a lot for your answers...