A charge `q` is placed at the some distance along the axis of a uniformly charged disc of surface cahrge density `sigma`. The flux due to the charge `q` through the disc is `phi`. The electric force on charge `q` exerted by the disc is
A. `sigmaphi`
B. `(sigmaphi)/(4pi)`
C. `(sigmaphi)/(2pi)`
D. `(sigmaphi)/(3pi)`