Text-based stimulus: Network-style diagram for item 70 with a router queue drawn as five boxes from front to rear. It shows packets or nodes labeled DB, AI; add an incoming arrow to the rear and outgoing arrow from the front. A course-prerequisite explorer uses BFS on a small dependency map. A breadth-first traversal uses a FIFO queue. Neighbor order is: CS0: CS1, DS1; CS1: ALG; DS1: DB, AI; ALG:; DB:; AI:. Start by enqueueing CS0. After 4 dequeue-and-expand step(s), which trace is correct?