[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is an organoarsonic acid anion. It is a conjugate base of a methylarsonic acid. It is a conjugate acid of a methylarsonate(2-)."}, {"from": "gpt", "value": "[C][As][=Branch1][C][=O][Branch1][C][O][O-1]"}]