Attempt Number: 2
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
Block `d` is already on top of block `b`, so we should stack block `a` on block `d` to achieve the goal state.

New State Description:
Block `a` is on block `d` and clear. Block `b` is on the table and not clear, supporting block `d`. Block `c` is on the table and clear. Block `d` is on block `b` and not clear, supporting block `a`. The hand is empty.

Action Chosen:
stack(a, d)
