Dr Gulshan S. answered 11/15/20
PhD In Physics and experience of teaching IB Physics and Math High sc
Her mg = W and F = W
Asd the body is about to move up
Force of friction ACTS downwards along the p[lane
Normal reaction = W cos theta
Force of friction = µs W cos theta
Force along the plane downwards = W Sin theta
So eqation of motion is
µs W cos theta + W sin theta = W.... Equation 1
Dividing by Wcos theta
µs + tan theta = 1/ cos theta = Sec theta
So answer a is correct choice