You can use navigational equipment or ground references to identify Class B boundaries by,
A) Monitoring your position using GPS or VOR/DME navigation and referencing Class B airspace charts.
B) Recognizing prominent landmarks or visual cues such as highways, rivers, or cities that delineate the Class B airspace boundaries.
C) Listening to ATC communications on the appropriate frequency and noting when you enter or exit the Class B airspace.
D) All of the above.