Correct Answer - 4
Resistance of bulb is `R = (100 xx 100)/(100) = Omega`
Rated current is `(100)/(100) = 1A`
In ac, `I_("rms") = (V_("rms"))/(Z) , Z = 200 Omega`
`sqrt(100^(2) + (omega L)^(2)) = 200 implies omega^(2) L^(2) = 30000` and
`L = sqrt((30000)/((100 pi)^(2))) = (sqrt(3))/(pi)` henry.