suppose you have ql as integer queue with the following data [1,2,3,4,5,6), where 1 is at the front of the queue and q1 is passed to a recursive method fl (), what the output of executing f1()? void fl( Lqueue ql ) { System.out.print (ql.dequeue()); if (!ql.isEmpty()) fi( q1); } Select one: O a. 1,2,3,4,5,6 b. 6,5,4,3,2,1 O c. method f1() is not executable Od 1,6,2,5,3,4