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 stack block 'd' on top of block 'b'. Since the hand is empty, the next logical step is to pick up block 'd' from the table to enable stacking it on block 'b'.

New State Description:
Block 'a' is on the table and clear. Block 'b' is on the table and clear. Block 'c' is on the table and clear. Block 'd' is in the hand and no longer clear. The hand is holding block 'd'.

Action Chosen:
pick-up(d)
