The correct decreasing order of priority for the functional groups of organic compounds in the IUPAC system of nomenclature is

For the following three reactions a, b and c, equilibrium constants are given:
a. CO (g) + H₂O (g) $$\leftrightharpoons$$ CO₂(g) + H₂ (g) ; K₁
b. CH₄ (g) + H₂O (g) $$\leftrightharpoons$$ CO(g) + 3H₂ (g) ; K₂
c. CH₄ (g) + 2H₂O (g) $$\leftrightharpoons$$ CO₂(g) + 4H₂ (g) ; K₃

The pK_a of a weak acid, HA, is 4.80. The pK_b of a weak base, BOH, is 4.78. The pH of an aqueous solution of the corresponding salt, BA, will be

Four species are listed below
i. $$HCO_3^−$$
ii. $$H_3O^+$$
iii. $$HSO_4^−$$
iv. $$HSO_3F$$
Which one of the following is the correct sequence of their acid strength?