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

Action Reasoning:
To progress towards the goal state, we should stack block 'd' on block 'c', as block 'c' is clear and block 'd' is currently held in the hand, which aligns with the goal state's requirement of 'd' being on 'c'.

New State Description:
Block 'a' is on the table and clear. Block 'c' is on top of block 'b' and not clear. Block 'b' is on the table. Block 'd' is on top of block 'c' and clear. The hand is empty. In the diagram, block 'd' is now stacked on block 'c', and the hand is empty.

Action Chosen:
stack(d, c)
