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

Action Reasoning:
To progress towards the goal state, we need to clear block `b`. Currently, block `c` is on `b` and needs to be removed. Picking up block `c` prepares it for moving elsewhere, making `b` clear, which is necessary for `d` to be placed directly on it.

New State Description:
Block `a` is on the table and clear. Block `b` is on the table and clear, since `c` is no longer on it. Block `c` is now in the hand and is no longer clear. Block `d` is on the table and clear. The hand is holding block `c`.

Action Chosen:
unstack(c, b)
