Attempt Number: 3
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 'b' on block 'c', which is currently clear. Since block 'b' is held by the hand, the next best action is to stack 'b' on 'c'.

New State Description:
Block 'a' is on top of block 'd', block 'b' is on top of block 'c', block 'c' is on the table and supporting block 'b', and block 'd' is on the table and supporting block 'a'. The hand is empty, as block 'b' has been stacked onto block 'c'.

Action Chosen:
stack(b, c)
