A solution is 20% alcohol by volume. If 10 mL of pure alcohol are added to 90 mL of this solution, what is the new percentage of alcohol by volume?

✓ Correct Answer: Option B

Initial alcohol: 20% of 90 mL = 18 mL. After adding 10 mL of alcohol, total alcohol becomes 18 + 10 = 28 mL. Total volume becomes 90 + 10 = 100 mL. New percentage = (28/100) * 100% = 28%.