Attempt Number: 2
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, block A needs to be stacked on block B. The hand is empty, block A is on the table and clear, and block B is clear, making "pick-up block_a" viable while also advancing towards the goal.

New State Description:
Block A is held by the hand and no longer clear. Block B is on block D and clear. Block C is on the table and not clear, with block D stacked on it. Block D is on block C and not clear. The table supports blocks A and C. The hand is not empty, holding block A.

Action Chosen:
pick-up(block_a)
