last qn in the vedio lesson for this topic has not been answered

i have not understood which qs u r talking about. still if it is the last one in the 1st part: then the answer is : 1 and three where net torque is not 0. here u have to consider the direction of the torque due to each force applied.in the 2nd case they r equal and oppposite, where in the 3 rd casae they  r in the same direction. in the 1st case they are in same direction.