Final answer:
The correct answer is that both branches and loops can be specified in a UML Sequence Diagram, represented by alt combined fragments for branches and loop combined fragments for loops.
Step-by-step explanation:
The correct statement is a. In UML Sequence Diagram both branches and loops can be specified. UML (Unified Modeling Language) sequence diagrams are used to model the dynamic aspects of a system. They depict the sequence of messages flowing from one object to another and can represent complex control structures like loops (repetition) and branches (conditional paths).
Loops are typically represented using a loop combined fragment, which is a visual mechanism to depict repetition in the interacting messages. Branches, on the other hand, are shown using an alt combined fragment, which is used to describe conditional flows in the sequence. These constructs make it possible to model a variety of scenarios that involve decision making and repetition within UML sequence diagrams.