Insoluble base reacts with dilute acid with: 

The fact that insoluble or soluble reactants can become soluble salts when they react with acid is the key to the solution. Titration is carried out in this instance, but only for one case. Here, a base—which might be either a metal oxide or a metal carbonate—is utilised as the insoluble reactant.

The acid-base reactions have been covered in our lower-level chemistry classes. We have also researched the fact that salt and other byproducts are produced when an acid and a base react. Acid interacts with an insoluble base or other reactants to produce salt, which is naturally soluble.

When an acid is combined with a suitably insoluble reactant, soluble salts are created. A metal oxide, a metal carbonate, or just a metal may be utilised as the insoluble reactant (base) in this situation. Depending on the specific salt needed, an insoluble base is employed in this situation.
For instance, in order to create copper salt, we must react dilute acids with copper oxide or carbonate. With weak acids, only copper metal does not produce copper salts. When we combine acid and metal, we create flammable hydrogen.

Dilute acid and powdered insoluble base are added to the container to create the soluble salt from the acids and insoluble base, which creates effervescence. After filtering the mixture to remove any extra powder, let the mixture out for a while to allow the water to evaporate, resulting in pure salt.
Filtering is carried out in order to completely eliminate the unreacted insoluble base from the mixture.
After all the insoluble reactants have been eliminated by filtration, all that is left are soluble salt and water, and after the water has evaporated, all that is left is pure salt. The response that is occurring is,

$\mathrm{CuO}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{CuSO}}_4+{\mathrm{H}}_2\mathrm{O}$

As a result, when an insoluble base combines with a diluted acid, water and soluble salts are produced.

Hence option A is correct.