ANS:C - thickness of the concrete topping 0d) half the thickness of the rib

The thickness of the flange of a Tee beam of a ribbed slab is typically assumed to be half the thickness of the rib. In a ribbed slab, the Tee beam is formed by the top portion of the rib. The flange of the Tee beam refers to this top portion, which extends horizontally and provides support to the slab. Since the thickness of the rib represents the vertical dimension of the Tee beam, it's common practice to assume that the flange thickness is half of this dimension. This assumption helps maintain an appropriate balance between the structural efficiency of the beam and the overall load-carrying capacity of the ribbed slab system. Therefore, the correct option is: half the thickness of the rib.