Let F be the force acting on a particle having position vector r vector and T vector be the torque of this force about the origin.  Then

(a) r vector X T vector=0  and F vector X T vector =0

(b) r vector X T vector = 0 and F vector x T vector not equal to Zero

(c) r vector X T vector not equal to zero and F vector X T vector = 0

(d) r vector x T vector not equal to zero and F vector x t vector not equal zer0

Ans.a

(10)