Attempt Number: 3
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 where block C is on top of block B, we first need to clear block C by unstacking B from C. This will allow us to stack C on B in the future.

New State Description:
Block b is held in the hand and is no longer on block c. Block c is clear and on the table. Block a is on the table and clear. Block d is on the table and clear. The hand is not empty.

Action Chosen:
unstack(b, c)
