Solve this :


$$\begin{gathered} 12. Which of the following forces are conservative\hspace{0.17em}? (x, y are coordinates in free space and \overrightarrow{r} is a position vector) \\ \left(A\right) \overrightarrow{F} = y\hat{i} + xj \left(B\right) \overrightarrow{F} = \frac{x}{\sqrt{x^2 + y^2}}\hat{i} + \frac{y}{\sqrt{x^2 + y^2}}\widehat{ j} \\ \left(C\right) \overrightarrow{F} = k\overrightarrow{r} \left(D\right) None of these \end{gathered}$$