Question

A reaction between which two reactants will consistently yield a salt that forms an acidic solution?

a weak acid and a weak base
a strong acid and a weak base
a strong acid and a strong base
a weak acid and a strong base

Answer 1

Change weak acid/base to weak fighter and strong acid/base to a strong fighter.
Who will win the battle?

Obviously the stronger component will win out. Thus the acidic solution must be formed when a strong acid interacts with a weak base.

But why? pretty easy. A strong acid or base dissociates completely in solution while a weak acid or base is in equilibrium with its molecular form and ionic forms. So not all the weak acid or base is dissociated in solution. When the strong acid/base meets with a weak base/acid, there are more strong acid/base ions compared to weak base/acid so all of the weak base and acid ions will be consumed by the strong acid/base and introduce leftover of the strong acid/base.