Correct Answer - A::B::C

Here, point of suspension has an acceleration. `a = g sin theta` (down the plane). Further, `g` can be resolved into two components `g sin theta` (along the plane) and `g cos theta` (perpendicular to plane).

`:. g_(eff) = g - a = g + ( -a)`

Resultant of g and `-a` will be `g cos theta`.

`:. g_(eff) = g cos theta`

(perpendicular to plane)

`:. T = 2pi sqrt((l)/(|g_(eff)|)) = 2pi sqrt ((l)/(g cos theta)`