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 step towards achieving the goal state is to stack block 'a', which is currently in hand, onto block 'c'. This brings us closer to the goal as 'a' needs to be on 'c' according to the goal state.

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

Action Chosen:
stack(a, c)
