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: Casting back in his memory, Hanson could not recall seeing the rock slabs the night before. Choices: 1. Hanson remembered seeing the rock slabs the previous night. 2. Hanson was sure the rock slabs had not been there all along. 3. Looking back, Hanson could not remember seeing the rock slabs.
1