To Show a Set of Messages That May Be Optional

Q14: An actor is always outside of the

Q15: Synchronization bars are used to indicate looping

Q16: ​A unique set of internal activities within

Q17: On a sequence diagram,a message represents a

Q18: An oval indicates an embedded use case

Q20: Which is correct?​ <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB5681/.jpg" alt="Which is

Q21: A textual model that describes the processing

Q22: If the True/False condition on a message

Q23: Which model is most useful in developing

Q24: An arrow on a system sequence diagram