For the reversible reaction X(g) ⇌ Y(g), the concentrations of species X and Y were monitored. Curve I starts at 1.00 M and decreases to 0.25 M, while curve II starts at 0 M and increases to 0.75 M, after which both curves become flat. Which statement is most consistent with the data?
a) Curve I represents reactant X, and equilibrium is reached at the point where the two curves intersect.
b) Curve I represents product Y, and equilibrium is reached when both curves become flat.
c) Curve I represents reactant X, and equilibrium is reached when both curves become flat.
d) Curve II represents reactant X, and equilibrium is reached when both curves become flat.