Attempt Number: 2
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
The goal is to place block c on block a. Since block c is currently held in the hand and block a is clear, the best action is to stack c on a.

New State Description:
Block a is on block b and clear. Block c is on block a and clear. Block d is on the table and clear. The hand is empty. Block b is supporting block a.

Action Chosen:
stack(c, a)
