The pair of compounds which cannot exist together in solution isA.NaHCO3 and NaOHB.Na2CO3 and NaHCO3C.Na2CO3 and NaOHD.NaHCO3 and NaCl

The pair of compounds which cannot exist together in solution is A. NaHCO3 and NaOH.

Here's why:

NaHCO3 (Sodium bicarbonate) and NaOH (Sodium hydroxide) cannot exist together in solution because they react with each other. Sodium hydroxide is a strong base and sodium bicarbonate is a weak base. When they are mixed, the strong base (NaOH) will react with the weak base (NaHCO3) to produce water (H2O) and a salt (Na2CO3), according to the following reaction:

NaHCO3 + NaOH -> Na2CO3 + H2O

So, they cannot exist together in solution because they react with each other to form different compounds.