Excess zinc is added by a student to dilute hydrochloric acid at $25\,^\circ\text{C}$. The hydrogen gas formed is gathered and its volume is measured at room temperature and pressure. The results are then plotted on the graph and labelled curve X. The experiment is carried out again at $50\,^\circ\text{C}$, while every other condition is kept unchanged. Which graph shows the results at $50\,^\circ\text{C}$?