The reaction rate between magnesium and dilute hydrochloric acid is being studied. The equation is shown. $\text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$ A measured mass of magnesium is placed into an excess of dilute hydrochloric acid. The hydrochloric acid concentration and the volume of hydrogen given off are recorded at regular time intervals. Which pair of graphs accurately represents the experimental results?