Final answer:
The acid-base pair that would produce an equivalence point at pH=7.0 in a titration is HNO2/NH3.
Step-by-step explanation:
The acid-base pair that would produce an equivalence point at pH=7.0 in a titration is option C: HNO2/NH3. At the equivalence point, a strong acid reacts with a strong base to produce a neutral solution with a pH of 7.0. In this case, HNO2 is a weak acid and NH3 is a weak base, but in the presence of excess NH3, they form NH4+ and NO2-. The resulting solution is neutral with a pH of 7.0.