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

Action Reasoning:
The next best action is to stack(block_d, block_c) because this places block D on block C, aligning with the goal state of having D on top of C.

New State Description:
Block A is on the table and clear. Block B is on the table and clear. Block C is on the table and is no longer clear because block D is on top of it. Block D is on top of block C and clear. The hand is empty.

Action Chosen:
stack(block_d, block_c)
