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

Action Reasoning:
To make progress towards the goal, we should focus on freeing the hand by putting down block 'b', so we can then pick up block 'a' and stack it on block 'c'.

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

Action Chosen:
put-down(block_b)
