Given the task definition and input, reply with output. In this task, you're given a statement, and three sentences as choices. Your job is to determine which sentence clearly disagrees with the statement. Indicate your answer as '1', '2', or '3' corresponding to the choice number of the selected sentence.

Statement: AC is assumed to be the principal reagent used to absorb the mercury in the exhaust gases. Choices: 1. Exhaust gases are where you need to absorb most of the mercury during the process. 2. AC isn't used anymore, we moved to different reagents years ago. 3. We think AC is the main reagent used to absorb the mercury.
2