What is a lifeline?
(a) It is a frame consisting of a rectangle with a pentagon in its upper left-hand corner
(b) It is a rectangle containing an identifier with a dashed line extending below the rectangle
(c) It is a name compartment; the interaction is represented inside the rectangle
(d) None of the mentioned
The question was asked in a dream while sleeping
This interesting question is from UML Sequence Diagrams in section Unified Modelling Language of Software Architecture