Electric field atcentre O of semicircle of radius 'a' having linear charge density $\lambda$ given is given by O a

Question

( A ) $\frac{2\lambda}{\epsilon_0a}$
( B ) $\frac{\lambda}{\pi\epsilon_oa}$
( C ) $\frac{\lambda\pi}{\epsilon_oa}$
( D ) $\frac{\lambda}{2\pi\epsilon_oa}$