The Following Graph Shows the Kinetics Curves for the Reaction $\rightarrow$

The following graph shows the kinetics curves for the reaction of oxygen with hydrogen to form water:
O₂(g) + 2H₂(g) $\rightarrow$ 2H₂O(g) . Which curve is hydrogen?

A) the dashed curve
B) the gray curve
C) the black curve
D) either the gray or the black curve
E) Any of these curves could be hydrogen.