ANS:D - least of the above.

In structural engineering, T-beams are a type of reinforced concrete beam with a cross-section resembling the letter "T." The flange of a T-beam refers to the horizontal part of the cross-section, while the web (or stem) is the vertical part. When designing T-beams, it's essential to ensure that the flange width is adequate to provide sufficient strength and stiffness to resist bending and shear forces. Here's how each of the options relates to the flange width of a T-beam:

1. One-third of the effective span of the T-beam: This option suggests that the width of the flange should be limited to one-third of the effective span of the T-beam. While this criterion may provide a rough guideline for proportions, it does not consider other factors such as structural efficiency or shear transfer at the interface between the flange and the web.
2. Distance between the centers of T-beam: This option is not a common criterion for determining the width of the flange of a T-beam. The distance between the centers of adjacent T-beams may be relevant for spacing considerations in structural layouts but does not directly relate to the design of an individual T-beam's flange width.
3. Breadth of the rib plus twelve times the thickness of the slab: This option suggests a specific formula for determining the maximum allowable flange width. It considers the width of the rib (web) and adds twelve times the thickness of the slab to it. This criterion takes into account the dimensions of the T-beam's components and the surrounding slab.

Given these options, the most appropriate criterion for limiting the width of the flange of a T-beam would be: Breadth of the rib plus twelve times the thickness of the slab This criterion considers both the width of the rib (web) and the thickness of the slab, providing a practical and dimensionally relevant limitation on the flange width. Therefore, this option is the most suitable among those provided.