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, we need to stack blocks D, B, and A progressively on top of block C. Block D is currently already on C. The next step is to place block B on block D since both are clear and the hand is empty.

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

Action Chosen:
pick-up(block_b)
