## Precalculus (6th Edition)

Option $A$.
The mixture is made of only two ingredients, namely: $26\%$ acid and $34\%$ acid This means the resulting mixture's concentration wil range anywhere from $26\%$ to $34\%$. It cannot go lower than 26 percent nor go higher than 34 percent. Therefore, the concentration of the mixture can be $30\%$, $31\%$, and $33\%$. However, the concentration of the mixture cannot be $24\%$. The answer is Option $A$.