The circularity of the diameter will be limited by the runout tolerance when the runout tolerance value is smaller than the size tolerance, as it is more restrictive.
If the runout tolerance value is smaller than the size tolerance of the diameter, the circularity of the diameter will be limited by the runout tolerance. This is because runout tolerance is a combination of size, form (roundness or circularity), orientation, and location and is more restrictive than size tolerance alone.
When the runout tolerance is less than the size tolerance, any part produced within size tolerance but outside the runout tolerance is considered nonconforming. Therefore, in this situation, the runout tolerance will dictate the circularity of the part.
The answer to the student's question is: B) Runout Tolerance.