For an elementary chemical reaction, \({{A}_{2}}\begin{matrix} {{k}_{1}} \\ \rightleftharpoons \\ {{k}_{-1}} \\ \end{matrix}2A,\) the expression for \(\frac{d\left[ A \right]}{dt}\) is

• A. 2k1 [A2] – k-1 [A]2
• B. k1 [A2] – k-1 [A]2
• C. 2k1 [A2] – 2k-1 [A]2
• D. k1 [A2] + k-1 [A]2