Ahorizontal platform in the form of a disk is supported only at its center a man of mass m, originally at rest at a distance d from the center, begins to walk with uniform velocity v in the circumferential direction, stopping after an interval of time t. plot the torque exerted on the support as a function of time

Please see the attached Figure

Explanation:

The torque exerted on the disk support will be the multiplication of the force applied (the person weight=mg) and the distance d of the person to the disk support (notice this distance is in the radial direction). Considering torque To=F*d*sen(90°)=F*d (90° is formed by the weight and the radial direction).  

The person begins walking to the circumferential direction, which means the constant velocity has also radial direction.  

If we consider d=D+r, being r the distance walked by the person and dr its differential. We can say dr=v*dt, and if we consider t=0 the time the person begins walking and a constant velocity, we have r=v*t from t=0 to t=T.

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

there are no contact forces mentioned on the list of choices that you've provided.