Question text    Identify the pair of compounds that represents a buffer solution:     ?

A buffer solution is a solution of weak acid and its salt (conjugate base of the weak acid).
A, B and D are false because H₂SO₄, HClO₄ and HCl are strong acids.
C is true because HNO₂ is a weak acid and NaNO₂ is its salt.

The answer: C. HNO₂/NaNO₂

weak acid or weak base PLUS the salt of that acid or base

(A).. is H2SO4 a weak acid or a weak base?  NO
(B).. is HClO4 (perchloric acid) a weak acid?  YOU answer
(C).. is HNO2 (nitrous acid) a weak acid?  you answer
(D).. is HCl a weak acid?  you answer

I just eliminated at least 2 choices for you.  if you don't know if HClO4 or HNO2 is the weak acid.. get to googling.