For $\mathrm{A}+\mathrm{B}\to \mathrm{products}$ the proposed mechanism is: step 1, $\mathrm{A}+\mathrm{B}\rightleftharpoons \mathrm{C}$ (fast, equilibrium); step 2, $\mathrm{C}+\mathrm{A}\to \mathrm{products}$ (slow). The rate law consistent with this mechanism is

1. Arate $=k[\mathrm{A}{]}^2[\mathrm{B}]$
2. Brate $=k[\mathrm{A}][\mathrm{B}]$
3. Crate $=k[\mathrm{C}]$
4. Drate $=k[\mathrm{A}][\mathrm{B}{]}^2$