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

Action Reasoning:
To achieve the goal state, block D should first be moved onto block C. This can be done by placing block A (currently held by the hand) onto block B, so that the hand becomes empty to execute further steps.

New State Description:
Block A is now on block B and is clear. Block B remains on block D and is not clear. Block C is clear on the table. Block D is not clear on the table. The hand is empty.

Action Chosen:
stack(block_a, block_b)
