Attempt Number: 2
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, I need to stack Block B onto Block D, moving closer to placing Block A last as the topmost block.

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, supporting block D. Block D is on block C and not clear, supporting block B. The hand is empty.

Action Chosen:
stack(block_b, block_d)
