Final answer:
The exact floor of Class B airspace at Dallas Executive Airport (RBD) cannot be determined without access to the specific aviation chart (Figure 25, Area 3). However, in typical charts, Class B airspace can start at either the surface, 3,000 feet MSL, or 3,100 feet MSL, depending on the specific airport and airspace configuration as depicted on the chart.
Step-by-step explanation:
The question is related to interpreting aviation charts, specifically Class B airspace boundaries for Dallas Executive Airport (RBD). Looking at the referenced airspace chart (which is not accessible here, but based on typical Class B airspace configurations), we can infer answers to the question and the airspace floor. Class B airspaces are often depicted as layered shelves, with the floor of the airspace at various altitudes. The question requires knowing the exact chart to give an accurate answer. If Dallas Executive Airport is depicted with its own airspace segment within Class B, the floor could either start at the surface if RBD is covered fully by Class B, or at a higher altitude specified on the chart if it lies under a higher shelf of the Class B airspace.
Without direct access to the chart (Figure 25, Area 3), the precise answer cannot be given. However, options 1) 'at the surface', 2) '3,000 feet MSL', and 3) '3,100 feet MSL' reflect possible altitudes where Class B airspace floors often begin. In standard charts, these figures are depicted amongst sectional chart symbols indicating the vertical boundaries of controlled airspace around airports.