JEE Advanced 2026 · Paper 1, Chemistry question 2

For a reversible reaction $\mathbf R\rightleftharpoons\mathbf P$, at constant temperature, both the forward and the backward reactions are first order elementary reactions with rate constants $k_f$ and $k_b$, respectively. At time zero, the concentration of $\mathbf R$ is $[\mathbf R]_0$ and the concentration of $\mathbf P$ is zero. At any given time, $[\mathbf R]$ and $[\mathbf P]$ are the concentrations of $\mathbf R$ and $\mathbf P$, respectively. If $k_b=4k_f$, the correct graphical representation of the reaction is