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

Action Reasoning:
To align with the goal state, the next best action is to stack block 'd' on block 'c', as block 'c' is clear and 'd' is held.

New State Description:
Block 'a' is on the table and clear. Block 'c' is on top of block 'b' and supporting block 'd'. Block 'b' is on the table. Block 'd' is on block 'c' and clear. The hand is empty.

Action Chosen:
stack(d, c)
