Which fragment models optional behavior that occurs only if a guard evaluates to true?

Which fragment models optional behavior that occurs only if a guard evaluates to true?

• A. opt combined fragment
• B. alt combined fragment
• C. loop combined fragment
• D. parallel combined fragment

Answer: (A)

The ability to model optional behavior that runs only when a guard is true is shown by the opt combined fragment. In UML sequence diagrams, the opt operator encloses interactions that may or may not occur depending on the guard condition. If the guard evaluates to true, the inside messages execute; if false, that fragment is skipped entirely. This precisely captures “optional behavior gated by a condition.” Other fragments work differently: the alt fragment represents mutually exclusive paths chosen based on guards, loop repeats the enclosed behavior, and the parallel fragment runs parts concurrently.

The ability to model optional behavior that runs only when a guard is true is shown by the opt combined fragment. In UML sequence diagrams, the opt operator encloses interactions that may or may not occur depending on the guard condition. If the guard evaluates to true, the inside messages execute; if false, that fragment is skipped entirely. This precisely captures “optional behavior gated by a condition.”

Other fragments work differently: the alt fragment represents mutually exclusive paths chosen based on guards, loop repeats the enclosed behavior, and the parallel fragment runs parts concurrently.