Attempt Number: 3
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
To move closer to the goal state, we need to rearrange the blocks so 'c' is on the table, 'a' is on 'c', 'b' is on 'a', and 'd' is on 'b'. Since 'd' is clear and on 'b', we should move 'd' to 'a' to eventually free 'b'.

New State Description:
The hand is now holding block 'd'. Block 'b' is clear and on the table. Block 'a' is on block 'c', and block 'c' is on the table. The diagram will show block 'd' in the hand, and 'b' alone on the table.

Action Chosen:
unstack(d, b)
