Arrange the acids

Question

I) hydrogen selenate ion (HSeO−
4
),
pKa = 1.92;
II) phosphorous acid (H3PO3),
pKa1 = 2.00;
III) phosphoric acid (H3PO4), pKa = 2.12;
IV) selenous acid (H2SeO3), pKa = 2.46;
in increasing order of strengths.
1. IV, III, II, I
2. II, IV, III, I
3. I, III, II, IV
4. I, III, IV, II
5. IV, II, III, I
6. None of these
7. III, IV, II, I
8. I, II, III, IV
9. Cannot be determined
10. I, II, IV, III

Answer 1

pk of 1 is stronger than pk of 2 is stronger than pk 9, etc. That should make it easy to arrange.