Task: Question Answering
Input (English): Question: Some of the 50% solution of acid was removed and this was replaced with an equal amount of 20% solution of acid. As a result, a 35% solution of acid was obtained. What fraction of the original solution was replaced?

 Option A: 1/3

 Option B: 1/2

 Option C: 2/3

 Option D: 3/5

 Option E: 4/7
Output (English): Option B