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, we must eventually have block c on the table. Since block c is currently clear, unstacking it from block b will help transition towards the goal state.

New State Description:
Block a is on the table. Block b is on top of block a. Block c is in the hand. Block d is on the table. Block b is clear. The hand is not empty.

Action Chosen:
unstack(c, b)
