A proposed three-step mechanism for the gas-phase reaction \[ \text{X}(g) \rightarrow \text{Z}(g) \] proceeds via two reaction intermediates, \( \text{Y}_1(g) \) and \( \text{Y}_2(g) \), through transition states \( \text{TS}_1 \), \( \text{TS}_2 \), and \( \text{TS}_3 \). The potential energy profile for the reaction is shown below.

Which of the following correctly ranks the species from greatest to least thermodynamic stability, and identifies the rate-determining step for the forward reaction?