The concentration of acid in solutions A, B and C are 4%, 2% and 2%, r

Since this question has no takers, here's my solution....

Useful property: If EQUAL VOLUMES of two solutions are combined, then the concentration of the resulting mixture will be equal to the AVERAGE of the two concentrations that were combined.
For example, if we combine 1 liter of 20% salt solution with 1 liter of 50% salt solution, the concentration of the resulting mixture will equal 35%, which is the average of 20% and 50%

We can apply that property here....

We'll start by combining 2 liters of solution A (4% acid) with 2 liters of solution C (2% acid).
Since we're combining EQUAL VOLUMES, the resulting mixture will be 3% acid (which is the average of 4% and 2%).
Note: The resulting mixture has 4 liters of solution (since we combined 2 liters of solution A with 2 liters of solution C)

From here, we'll combine the 4 liters of resulting solution (3% acid) with 4 liters of solution B (2% acid).
Once again, since we're combining EQUAL VOLUMES, the resulting mixture will be 2.5% acid (which is the average of 3% and 2%)

Answer: B