ANS:E - all the above.

1. Breadth of the rib: The width of the flange of a T-beam is influenced by the breadth of the rib because the rib supports the flange. A wider rib provides more support to the flange, allowing it to effectively act as part of the T-beam structure.
2. Overall thickness of the rib: While the thickness of the rib is important for its structural integrity, it doesn't directly influence the width of the flange that effectively acts with the rib. The width of the rib is the primary factor in determining how much support it provides to the flange.
3. Centre to centre distance between T-beams: The center-to-center distance between T-beams is relevant for determining the spacing and arrangement of multiple T-beams in a structure. It doesn't directly affect the width of the flange that interacts with the rib.
4. Span of the T-beam: The span of the T-beam refers to the distance between its supports. While the span influences the overall design and load-bearing capacity of the T-beam, it doesn't directly impact the width of the flange that interacts with the rib.