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

Action Reasoning:
To achieve the goal state, we need to place block 'd' on block 'c' and then stack block 'a' on block 'b'. Since block 'd' is currently held, the next logical step is to stack it on block 'c', which is clear.

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

Action Chosen:
stack(d, c)
