Three pieces of potato, all of the same size, were placed in sucrose solutions of different concentrations. A single piece of potato was placed in distilled water. The sucrose solution concentrations were $0.2\,\text{g dm}^{-3}$, $0.4\,\text{g dm}^{-3}$ and $0.6\,\text{g dm}^{-3}$. The graph shows how the mass of the potato pieces changed during a period of $60$ minutes. Which piece of potato was placed in distilled water?