Attempt Number: 2
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 should first pick up block C since it is clear and on the table. This prepares us to stack it on block A.

New State Description:
Block a is on the table and clear, block b is on the table and clear, block d is on the table and clear. Block c is held by the hand. The diagram now shows block c being held above the table.

Action Chosen:
pick-up(c)
