Attempt Number: 4
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
Block B is currently held by the hand. To progress towards the goal, Block B should be stacked onto Block D, which is clear. This action positions Block B closer to its goal location on top of Block D, aligning with part of the final stack formation.

New State Description:
Block A is on the table and clear. Block B is on block D and clear. Block C is on the table and not clear, with block D stacked on it. Block D is on block C and not clear. The hand is empty.

Action Chosen:
stack(block_b, block_d)
