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

Action Reasoning:
To proceed towards the goal state, we need to free the blocks below block b. Unstacking block b from block c is the initial step, allowing us to manipulate other blocks.

New State Description:
The hand is holding block b. Block c is now clear since block b is no longer on top of it. Block a is on the table. Block d is on top of block a. Block c is on top of block d. The hand is no longer empty.

Action Chosen:
unstack(b, c)
