Attempt Number: 4
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
Currently, block 'd' is in the hand, and we want to stack 'd' on 'a' as part of our goal state. Since 'a' is clear and on the table, we can perform the stack action to place 'd' on 'a'.

New State Description:
The hand is empty. Block 'd' is on top of block 'a'. Block 'a' is no longer clear because it supports block 'd'. Block 'b' is clear and on the table. Block 'c' is clear and on the table.

Action Chosen:
stack(d, a)
