Rate constant of the first-order reaction when initial concentration $C_{0}$ and concentration $C_{t}$ at time $t$ is given by equation:
$k_{t}=\log C_{0}-\log C_{t}$
Graph is a straight line if we plot
(a) $\mathrm{t} \operatorname{vs} \log \mathrm{C}_{\mathrm{o}}$
(b) $\mathrm{t} \mathrm{vs} \log \mathrm{C}_{\mathrm{t}}$
(c) $\mathrm{t}^{-1} \operatorname{vs} \log \mathrm{C}_{\mathrm{t}}$
(d) $\log C_{o} \operatorname{vs} \log C_{t}$