If `theta_1,theta_2,theta_3` are the three values of `thetain[0,2pi]` for which `tantheta=lambda` then the value of `tan(theta_1)/3tan(theta_2)/3+tan(theta_2)/3tan(theta_3)/3+tan(theta_3)/3tan(theta_1)/3` is equal to
A. `1//3`
B. 1
C. 3
D. none of these