By applying BFS algorithm
first we enter P in Queue and process it now we add neighbors of P that are Q and R in any order, since all the options have Q as 2nd element first we enqueue Q then R
Queue have |R|Q|
now we process Q and add its neighbors
Queue have |T|R|
process R
queue have |S|M|T|
process T
Queue have |U|N|S|M|
now no new vertex will be added
so PQRTMSNU