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 Block A, we need to first clear Block C by removing Block D. Unstacking Block D from Block C is the necessary first step.

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

Action Chosen:
unstack(d, c)
