Attempt Number: 3
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, we need to place block 'b' on block 'c' which is clear and on the table. The best action is to stack 'b' on 'c'.

New State Description:
Block 'a' is on top of block 'd' and is clear. Block 'c' is on the table and now supports block 'b'. The hand is empty, and block 'b' is no longer held.

Action Chosen:
stack(b, c)
