Attempt Number: 4
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 'a'. The hand is empty, and block 'd' is clear on the table, so the first step should be to pick up block 'd'.

New State Description:
The hand is holding block 'd'. Block 'a' is on top of block 'c'. Block 'b' is clear and remains on the table. Block 'c' is supporting block 'a' and is on the table. The hand is no longer empty.

Action Chosen:
pick-up(d)
