In given figure, the current `(//)` is flowing through straight wire annd divided equally in two loops as shown in the figure. The magnitude field intensity at center (O) is

Options

A. Zero
B. `((underset(0)(mu)//)/8[1/underset(2)(r)-1/underset(1)(r)])`
C. `((underset(0)(mu)//)/(4pi)[pi/underset(2)(2r)-pi/underset(1)(2r)-1/underset(1)(r)])`
D. `((underset(0)(mu)//)/(4pi)[pi/underset(2)(2r)-pi/underset(1)(2r)+pi/underset(1)(r)])`