Two semicircular rings lying in the same plane of uniform linear charge density \[\lambda \] have radii r and 2r. They are joined using two straight uniformly charged wires of linear charge density \[\lambda \] and length r as shown in the figure. The magnitude of electric field at common centre of semi-circular rings is

• A. \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{3\lambda }{2r}\]                      
• B. \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{\lambda }{2r}\]
• C. \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{2\lambda }{r}\]
• D. \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{\lambda }{r}\]