Answer:
Option A
Explanation:
We have differential equation
$\frac{d\theta}{dt}=-k(\theta-\theta_{0})$ , where k is constant
$\Rightarrow$ $\frac{d\theta}{dt}+k\theta=k\theta_{0}$
which is linear differential equation in the form of
$\Rightarrow$ $\frac{dy}{dx}+Py=Q$
$\therefore$ $IF= e^{\int kdt }=e^{kt}$
therefore required solution,
$(\theta)(e^{kt})=\int(e^{kt}\times k \theta_{0})dt$
$\Rightarrow$ $\theta e^{kt}=e^{kt}\theta_{0}+a$
$\Rightarrow$ $\theta =\theta_{0}+ae^{-kt}$