Attempt Number: 2
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 need to stack block 'a' on block 'c', which is clear and on the table. This action aligns with the goal and sets up the foundation for stacking 'd' on 'a'.

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

Action Chosen:
stack(a, c)
