Attempt Number: 3
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 place block 'a' onto block 'd', which is clear and on the table. Since the hand is currently holding block 'a', we can stack 'a' onto 'd' to match the goal configuration.

New State Description:
Block 'a' is stacked on top of block 'd', which is on the table. Block 'd' is now supporting block 'a'. Block 'c' remains on top of block 'b', and block 'b' is supporting block 'c'. The hand is now empty.

Action Chosen:
stack(a, d)
